Catalysts for petrochemical catalysis

ABSTRACT

Metal oxide catalysts comprising various dopants are provided. The catalysts are useful as heterogenous catalysts in a variety of catalytic reactions, for example, the oxidative coupling of methane to C2 hydrocarbons such as ethane and ethylene. Related methods for use and manufacture of the same are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/479,767, filed on May 24, 2012 now U.S. Pat. No. 8,921,256,which claims the benefit under 35 U.S.C. §119(e) of U.S. ProvisionalPatent Application No. 61/489,651 filed on May 24, 2011 and U.S.Provisional Patent Application No. 61/564,832 filed on Nov. 29, 2011,which applications are incorporated herein by reference in theirentireties.

BACKGROUND

1. Technical Field

This invention is generally related to novel catalysts and, morespecifically, to doped metal oxide catalysts useful as heterogeneouscatalysts in a variety of catalytic reactions, such as the oxidativecoupling of methane to C2 hydrocarbons.

2. Description of the Related Art

Catalysis is the process in which the rate of a chemical reaction iseither increased or decreased by means of a catalyst. Positive catalystsincrease the speed of a chemical reaction, while negative catalysts slowit down. Substances that increase the activity of a catalyst arereferred to as promoters or activators, and substances that deactivate acatalyst are referred to as catalytic poisons or deactivators. Unlikeother reagents, a catalyst is not consumed by the chemical reaction, butinstead participates in multiple chemical transformations. In the caseof positive catalysts, the catalytic reaction generally has a lowerrate-limiting free energy change to the transition state than thecorresponding uncatalyzed reaction, resulting in an increased reactionrate at the same temperature. Thus, at a given temperature, a positivecatalyst tends to increase the yield of desired product while decreasingthe yield of undesired side products. Although catalysts are notconsumed by the reaction itself, they may be inhibited, deactivated ordestroyed by secondary processes, resulting in loss of catalyticactivity.

Catalysts are generally characterized as either heterogeneous orhomogeneous. Heterogeneous catalysts exist in a different phase than thereactants (e.g. a solid metal catalyst and gas phase reactants), and thecatalytic reaction generally occurs on the surface of the heterogeneouscatalyst. Thus, for the catalytic reaction to occur, the reactants mustdiffuse to and/or adsorb onto the catalyst surface. This transport andadsorption of reactants is often the rate limiting step in aheterogeneous catalysis reaction. Heterogeneous catalysts are alsogenerally easily separable from the reaction mixture by commontechniques such as filtration or distillation.

In contrast to a heterogeneous catalyst, a homogenous catalyst exists inthe same phase as the reactants (e.g., a soluble organometallic catalystand solvent-dissolved reactants). Accordingly, reactions catalyzed by ahomogeneous catalyst are controlled by different kinetics than aheterogeneously catalyzed reaction. In addition, homogeneous catalystscan be difficult to separate from the reaction mixture.

While catalysis is involved in any number of technologies, oneparticular area of importance is the petrochemical industry. At thefoundation of the modern petrochemical industry is the energy-intensiveendothermic steam cracking of crude oil. Cracking is used to producenearly all the fundamental chemical intermediates in use today. Theamount of oil used for cracking and the volume of green house gases(GHG) emitted in the process are quite large: cracking consumes nearly10% of the total oil extracted globally and produces 200M metric tons ofCO₂ equivalent every year (Ren, T, Patel, M. Res. Conserv. Recycl.53:513, 2009). There remains a significant need in this field for newtechnology directed to the conversion of unreactive petrochemicalfeedstocks (e.g. paraffins, methane, ethane, etc.) into reactivechemical intermediates (e.g. olefins), particularly with regard tohighly selective heterogeneous catalysts for the direct oxidation ofhydrocarbons.

While there are multistep paths to convert methane to certain specificchemicals using first; high temperature steam reforming to syngas (amixture of H₂ and CO), followed by stochiometry adjustment andconversion to either methanol or, via the Fischer-Tropsch (F-T)synthesis, to liquid hydrocarbon fuels such as diesel or gasoline, thisdoes not allow for the formation of certain high value chemicalintermediates. This multi-step indirect method also requires a largecapital investment in facilities and is expensive to operate, in partdue to the energy intensive endothermic reforming step. For instance, inmethane reforming, nearly 40% of methane is consumed as fuel for thereaction. It is also inefficient in that a substantial part of thecarbon fed into the process ends up as the GHG CO₂, both directly fromthe reaction and indirectly by burning fossil fuels to heat thereaction. Thus, to better exploit the natural gas resource, directmethods that are more efficient, economical and environmentallyresponsible are required.

One of the reactions for direct natural gas activation and itsconversion into a useful high value chemical, is the oxidative couplingof methane (“OCM”) to ethylene: 2CH₄+O₂→C₂H₄+2H₂O. See, e.g., Zhang, Q.,Journal of Natural Gas Chem., 12:81, 2003; Olah, G. “HydrocarbonChemistry”, Ed. 2, John Wiley & Sons (2003). This reaction is exothermic(ΔH=−67 kcals/mole) and has typically been shown to occur at very hightemperatures (>700° C.). Although the detailed reaction mechanism is notfully characterized, experimental evidence suggests that free radicalchemistry is involved. (Lunsford, J. Chem. Soc., Chem. Comm., 1991; H.Lunsford, Angew. Chem., Int. Ed. Engl., 34:970, 1995). In the reaction,methane (CH₄) is activated on the catalyst surface, forming methylradicals which then couple in the gas phase to form ethane (C₂H₆),followed by dehydrogenation to ethylene (C₂H₄). Several catalysts haveshown activity for OCM, including various forms of iron oxide, V₂O₅,MoO₃, Co₃O₄, Pt—Rh, Li/ZrO₂, Ag—Au, Au/Co₃O₄, Co/Mn, CeO₂, MgO, La₂O₃,Mn₃O₄, Na₂WO₄, MnO, ZnO, and combinations thereof, on various supports.A number of doping elements have also proven to be useful in combinationwith the above catalysts.

Since the OCM reaction was first reported over thirty years ago, it hasbeen the target of intense scientific and commercial interest, but thefundamental limitations of the conventional approach to C—H bondactivation appear to limit the yield of this attractive reaction.Specifically, numerous publications from industrial and academic labshave consistently demonstrated characteristic performance of highselectivity at low conversion of methane, or low selectivity at highconversion (J. A. Labinger, Cat. Lett., 1:371, 1988). Limited by thisconversion/selectivity threshold, no OCM catalyst has been able toexceed 20-25% combined C₂ yield (i.e. ethane and ethylene), and moreimportantly, all such reported yields operate at extremely hightemperatures (>800 C).

In this regard, it is believed that the low yield of desired products(i.e. C₂H₄ and C₂H₆) is caused by the unique homogeneous/heterogeneousnature of the reaction. Specifically, due to the high reactiontemperature, a majority of methyl radicals escape the catalyst surfaceand enter the gas phase. There, in the presence of oxygen and hydrogen,multiple side reactions are known to take place (J. A. Labinger, Cat.Lett., 1:371, 1988). The non-selective over-oxidation of hydrocarbons toCO and CO₂ (e.g., complete oxidation) is the principal competing fastside reaction. Other undesirable products (e.g. methanol, formaldehyde)have also been observed and rapidly react to form CO and CO₂.

In order to result in a commercially viable OCM process, a catalystoptimized for the activation of the C—H bond of methane at lowertemperatures (e.g. 500-800° C.) higher activities, and higher pressuresare required. While the above discussion has focused on the OCMreaction, numerous other catalytic reactions (as discussed in greaterdetail below) would significantly benefit from catalytic optimization.Accordingly, there remains a need in the art for improved catalysts and,more specifically, catalysts for improving the yield, selectivity andconversion of, for example, the OCM reaction and other catalyzedreactions. The present invention fulfills these needs and providesfurther related advantages.

BRIEF SUMMARY

In brief, heterogeneous metal oxide catalysts and related methods aredisclosed. For example, catalysts comprising oxides of magnesium,manganese, tungsten and/or rare earth elements are provided. Thedisclosed catalysts find utility in any number of catalytic reactions,for example in the OCM reaction. In some embodiments, the catalysts areadvantageously doped with one or more doping elements. The dopingelements may be promoters such that the catalyst comprises an improvedcatalytic activity. For example, in certain embodiments, the catalyticactivity is such that the C2 selectivity is 50% or greater and themethane conversion is 20% or greater when the catalyst is employed as aheterogenous catalyst in the oxidative coupling of methane at atemperature of 850° C. or less, 800° C. or less, for example 750° C. orless or 700° C. or less.

In one embodiment, the disclosure provides a catalyst comprising a mixedoxide of magnesium and manganese, wherein the catalyst further compriseslithium and boron dopants and at least one doping element from groups 4,9, 12, 13 or combinations thereof, wherein the catalyst comprises a C₂selectivity of greater than 50% and a methane conversion of greater than20% when the catalyst is employed as a heterogenous catalyst in theoxidative coupling of methane at a temperature of 750° C. or less.

In another embodiment, a catalyst comprising a mixed oxide of manganeseand tungsten, wherein the catalyst further comprises a sodium dopant andat least one doping element from groups 2, 16 or combinations thereof isprovided.

In still another embodiment, the disclosure is directed to a catalystcomprising an oxide of a rare earth element, wherein the catalystfurther comprises at least one doping element from groups 1-16,lanthanides, actinides or combinations thereof, wherein the catalystcomprises a C₂ selectivity of greater than 50% and a methane conversionof greater than 20% when the catalyst is employed as a heterogenouscatalyst in the oxidative coupling of methane at a temperature of 750°C. or less.

In another embodiment, a catalyst comprising a mixed oxide of manganeseand tungsten, wherein the catalyst further comprises a sodium dopant andat least one doping element from groups 2, 4-6, 8-15, lanthanides orcombinations thereof, wherein the catalyst comprises a C₂ selectivity ofgreater than 50% and a methane conversion of greater than 20% when thecatalyst is employed as a heterogenous catalyst in the oxidativecoupling of methane at a temperature of 750° C. or less is provided.

In yet other embodiments, the disclosure provides a catalyst comprisinga mixed oxide of a lanthanide and tungsten, wherein the catalyst furthercomprises a sodium dopant and at least one doping element from groups 2,4-15, lanthanides or combinations thereof, wherein the catalystcomprises a C₂ selectivity of greater than 50% and a methane conversionof greater than 20% when the catalyst is employed as a heterogenouscatalyst in the oxidative coupling of methane at a temperature of 750°C. or less.

Other embodiments are directed to a catalyst comprising a rare earthoxide and one or more dopants, wherein the catalyst comprises a C₂selectivity of greater than 50% and a methane conversion of greater than20% when the catalyst is employed as a heterogenous catalyst in theoxidative coupling of methane at a temperature of 750° C. or less, andwherein the dopant comprises Eu/Na, Sr/Na, Na/Zr/Eu/Ca, Mg/Na,Sr/Sm/Ho/Tm, Sr/W, Mg/La/K, Na/K/Mg/Tm, Na/Dy/K, Na/La/Dy, Na/La/Eu,Na/La/Eu/In, Na/La/K, Na/La/Li/Cs, K/La, K/La/S, K/Na, Li/Cs, Li/Cs/La,Li/Cs/La/Tm, Li/Cs/Sr/Tm, Li/Sr/Cs, Li/Sr/Zn/K, Li/Ga/Cs, Li/K/Sr/La,Li/Na, Li/Na/Rb/Ga, Li/Na/Sr, Li/Na/Sr/La, Li/Sm/Cs, Ba/Sm/Yb/S,Ba/Tm/K/La, Ba/Tm/Zn/K, Cs/K/La, Cs/La/Tm/Na, Cs/Li/K/La, Sm/Li/Sr/Cs,Sr/Cs/La, Sr/Tm/Li/Cs, Zn/K, Zr/Cs/K/La, Rb/Ca/In/Ni, Sr/Ho/Tm, La/Nd/S,Li/Rb/Ca, Li/K, Tm/Lu/Ta/P, Rb/Ca/Dy/P, Mg/La/Yb/Zn, Rb/Sr/Lu,Na/Sr/Lu/Nb, Na/Eu/Hf, Dy/Rb/Gd, Na/Pt/Bi, Rb/Hf, Ca/Cs, Ca/Mg/Na,Hf/Bi, Sr/Sn, Sr/W, Sr/Nb, Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca, Bi/Sn,Bi/Sb, Ge/Hf, Hf/Sm, Sb/Ag, Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W, Sb/Hf,Sb/Yb, Sb/Sn, Yb/Au, Yb/Ta, Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag, Au/Sr,W/Ge, Ta/Hf, W/Au, Ca/W, Au/Re, Sm/Li, La/K, Zn/Cs, Na/K/Mg, Zr/Cs,Ca/Ce, Na/Li/Cs, Li/Sr, Cs/Zn, La/Dy/K, Dy/K, La/Mg, Na/Nd/In/K, In/Sr,Sr/Cs, Rb/Ga/Tm/Cs, Ga/Cs, K/La/Zr/Ag, Lu/Fe, Sr/Tm, La/Dy, Sm/Li/Sr,Mg/K, Li/Rb/Ga, Li/Cs/Tm, Zr/K, Li/Cs, Li/K/La, Ce/Zr/La, Ca/Al/La,Sr/Zn/La, Sr/Cs/Zn, Sm/Cs, In/K, Ho/Cs/Li/La, Cs/La/Na, La/S/Sr,K/La/Zr/Ag, Lu/Tl, Pr/Zn, Rb/Sr/La, Na/Sr/Eu/Ca, K/Cs/Sr/La, Na/Sr/Lu,Sr/Eu/Dy, Lu/Nb, La/Dy/Gd, Na/Mg/Tl/P, Na/Pt, Gd/Li/K, Rb/K/Lu,Sr/La/Dy/S, Na/Ce/Co, Na/Ce, Na/Ga/Gd/Al, Ba/Rh/Ta, Ba/Ta, Na/Al/Bi,Cs/Eu/S, Sm/Tm/Yb/Fe, Sm/Tm/Yb, Hf/Zr/Ta, Rb/Gd/Li/K, Gd/Ho/Al/P,Na/Ca/Lu, Cu/Sn, Ag/Au, Al/Bi, Al/Mo, Al/Nb, Au/Pt, Ga/Bi, Mg/W, Pb/Au,Sn/Mg, Zn/Bi, Gd/Ho, Zr/Bi, Ho/Sr, Gd/Ho/Sr, Ca/Sr, Ca/Sr/W,Na/Zr/Eu/Tm, Sr/Ho/Tm/Na, Sr/Pb, Ca, Sr/W/Li, Ca/Sr/W, Sr/Hf orcombinations thereof.

Still other catalysts of the present invention include a catalystcomprising a mixed oxide of a rare earth element and a Group 13 element,wherein the catalyst further comprises one or more Group 2 elements.

Other embodiments of the present invention are directed to a catalystcomprising a lanthanide oxide doped with an alkali metal, an alkalineearth metal or combinations thereof, and at least one other dopant fromgroups 3-16.

Methods for use of the disclosed catalysts in catalytic reactions, forexample OCM, are also provided. Furthermore, the present disclosure alsoprovides for the preparation of downstream products of ethylene, whereinthe ethylene has been prepared via a reaction employing a catalystdisclosed herein.

These and other aspects of the invention will be apparent upon referenceto the following detailed description. To this end, various referencesare set forth herein which describe in more detail certain backgroundinformation, procedures, compounds and/or compositions, and are eachhereby incorporated by reference in their entirety.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, the sizes and relative positions of elements in thedrawings are not necessarily drawn to scale. For example, the variouselements and angles are not drawn to scale, and some of these elementsare arbitrarily enlarged and positioned to improve drawing legibility.Further, the particular shapes of the elements as drawn are not intendedto convey any information regarding the actual shape of the particularelements, and have been selected solely for ease of recognition in thedrawings.

FIG. 1 schematically depicts a first part of an OCM reaction at thesurface of a metal oxide catalyst.

FIG. 2 shows a method for catalyst screening.

FIG. 3 schematically depicts a carbon dioxide reforming reaction on acatalytic surface.

FIG. 4 is a flow chart for data collection and processing in evaluatingcatalytic performance.

FIG. 5 is a chart showing various downstream products of ethylene.

FIG. 6 shows an OCM and ethylene oligomerization module.

FIG. 7 is a plot of conversion, selectivity and yield of an OCM reactioncatalyzed with a doped and undoped catalyst.

FIG. 8 is a plot of conversion, selectivity and yield of an OCM reactioncatalyzed comparing a catalyst on two different supports.

FIG. 9 depicts the results of high-throughput screening on a dopedCo/Na/LiMnMgB library.

FIG. 10 depicts the results of high-throughput screening on a dopedMnWO₄ on silica library.

FIG. 11 depicts the results of high-throughput screening on a dopedNd₂O₃ library.

FIG. 12 depicts the results of high-throughput screening on a dopedYb₂O₃ library.

FIG. 13 depicts the results of high-throughput screening on a dopedEu₂O₃ library.

FIG. 14 depicts the results of high-throughput screening on a dopedLa₂O₃ library.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various embodiments.However, one skilled in the art will understand that the invention maybe practiced without these details. In other instances, well-knownstructures have not been shown or described in detail to avoidunnecessarily obscuring descriptions of the embodiments. Unless thecontext requires otherwise, throughout the specification and claimswhich follow, the word “comprise” and variations thereof, such as,“comprises” and “comprising” are to be construed in an open, inclusivesense, that is, as “including, but not limited to.” Further, headingsprovided herein are for convenience only and do not interpret the scopeor meaning of the claimed invention.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. Thus, the appearances of the phrases “in one embodiment” or“in an embodiment” in various places throughout this specification arenot necessarily all referring to the same embodiment. Furthermore, theparticular features, structures, or characteristics may be combined inany suitable manner in one or more embodiments. Also, as used in thisspecification and the appended claims, the singular forms “a,” “an,” and“the” include plural referents unless the content clearly dictatesotherwise. It should also be noted that the term “or” is generallyemployed in its sense including “and/or” unless the content clearlydictates otherwise.

As discussed above, heterogeneous catalysis takes place between severalphases. Generally, the catalyst is a solid, the reactants are gases orliquids and the products are gases or liquids. Thus, a heterogeneouscatalyst provides a surface that has multiple active sites foradsorption of one more gas or liquid reactants. Once adsorbed, certainbonds within the reactant molecules are weakened and dissociate,creating reactive fragments of the reactants, e.g., in free radicalforms. One or more products are generated as new bonds between theresulting reactive fragments form, in part, due to their proximity toeach other on the catalytic surface.

As an example, FIG. 1 shows schematically the first part of an OCMreaction that takes place on the surface of a metal oxide catalyst 10which is followed by methyl radical coupling in the gas phase. A crystallattice structure of metal atoms 14 and oxygen atoms 20 are shown, withan optional dopant 24 incorporated into the lattice structure. In thisreaction, a methane molecule 28 comes into contact with an active site(e.g., surface oxygen 30) and becomes activated when a hydrogen atom 34dissociates from the methane molecule 28. As a result, a methyl radical40 is generated on or near the catalytic surface. Two methyl radicalsthus generated can couple in the gas phase to create ethane and/orethylene, which are collectively referred to as the “C2” couplingproducts.

It is generally recognized that the catalytic properties of a catalyststrongly correlate to its surface morphology. Typically, the surfacemorphology can be defined by geometric parameters such as: (1) thenumber of surface atoms (e.g., the surface oxygen of FIG. 1) thatcoordinate to the reactant; and (2) the degree of coordinativeunsaturation of the surface atoms, which is the coordination number ofthe surface atoms with their neighboring atoms. For example, thereactivity of a surface atom decreases with decreasing coordinativeunsaturation. For example, for the dense surfaces of a face-centeredcrystal, a surface atom with 9 surface atom neighbors will have adifferent reactivity than one with 8 neighbors. Additional surfacecharacteristics that may contribute to the catalytic properties include,for example, crystal dimensions, lattice distortion, surfacereconstructions, defects, grain boundaries, and the like. See, e.g., VanSanten R. A. et al New Trends in Materials Chemistry 345-363 (1997).

Advantageously, the catalysts disclosed herein and methods of producingthe same have general applicability to a wide variety of heterogeneouscatalyses, including without limitation: oxidative coupling of methane(e.g., FIG. 1), oxidative dehydrogenation of alkanes to theircorresponding alkenes, selective oxidation of alkanes to alkenes andalkynes, oxidation of carbon monoxide, dry reforming of methane,selective oxidation of aromatics, Fischer-Tropsch reaction, hydrocarboncracking, combustions of hydrocarbons and the like.

FIG. 2 schematically shows a high throughput work flow for generatinglibraries of diverse catalysts and screening for their catalyticproperties. An initial phase of the work flow involves a primaryscreening, which is designed to broadly and efficiently screen a largeand diverse set of catalysts that logically could perform the desiredcatalytic transformation. For example, certain doped metal oxides (e.g.,Mn, Mg, W, etc.) are known catalysts for the OCM reaction. Therefore,catalysts of various metal oxide compositions comprising various dopantscan be prepared and evaluated for their catalytic performances in an OCMreaction.

More specifically, the work flow 100 begins with designing syntheticexperiments for making various metal oxide compositions (block 110). Thesynthesis, subsequent treatments and screenings can be manual orautomated. As will be discussed in more detail herein, by varying thesynthetic conditions, catalysts can be prepared with various surfacemorphologies and/or compositions in respective microwells (block 114).The catalysts are subsequently calcined and then optionally doped (block120). Optionally, the doped and calcined catalysts are further mixedwith a catalyst support (block 122). Beyond the optional support step,all subsequent steps are carried out in a “wafer” format, in whichcatalysts are deposited in a quartz wafer that has been etched to createan ordered array of microwells. Each microwell is a self-containedreactor, in which independently variable processing conditions can bedesigned to include, without limitation, respective choices of elementalcompositions, catalyst support, reaction precursors, templates, reactiondurations, pH values, temperatures, ratio between reactants, gas flows,and calcining conditions (block 124). Due to design constraints of somewafers, in some embodiments calcining and other temperature variablesare identical in all microwells. A wafer map 130 can be created tocorrelate the processing conditions to the catalyst in each microwell. Alibrary of diverse catalysts can be generated in which each librarymember corresponds to a particular set of processing conditions andcorresponding compositional and/or morphological characteristics.

Catalysts obtained under various synthetic conditions and dopingcompositions are thereafter deposited in respective microwells of awafer (140) for evaluating their respective catalytic properties in agiven reaction (blocks 132 and 134). The catalytic performance of eachlibrary member can be screened serially by several known primaryscreening technologies, including scanning mass spectroscopy (SMS)(Symyx Technologies Inc., Santa Clara, Calif.). The screening process isfully automated, and the SMS tool can determine if a catalyst iscatalytically active or not, as well as its relative strength as acatalyst at a particular temperature. Typically, the wafer is placed ona motion control stage capable of positioning a single well below aprobe that flows the feed of the starting material over the catalystsurface and removes reaction products to a mass spectrometer and/orother detector technologies (blocks 134 and 140). The individualcatalyst is heated to a preset reaction temperature, e.g., using a CO₂IR laser from the backside of the quartz wafer and an IR camera tomonitor temperature and a preset mixture of reactant gases. The SMS toolcollects data with regard to the consumption of the reactant(s) and thegeneration of the product(s) of the catalytic reaction in each well(block 144), and at each temperature and flow rate.

The SMS data obtained as described above provide information on relativecatalytic properties among all the library members (block 150). In orderto obtain more quantitative data on the catalytic properties of thecatalysts, possible hits that meet certain criteria are subjected to asecondary screening (block 154). Typically, secondary screeningtechnologies include a single, or alternatively multiple channelfixed-bed or fluidized bed reactors (as described in more detailherein). In parallel reactor systems or multi-channel fixed-bed reactorsystem, a single feed system supplies reactants to a set of flowrestrictors. The flow restrictors divide the flows evenly among parallelreactors. Care is taken to achieve uniform reaction temperature betweenthe reactors such that the various catalysts can be differentiatedsolely based on their catalytic performances. The secondary screeningallows for accurate determination of catalytic properties such asselectivity, yield and conversion (block 160). These results serve as afeedback for designing further catalyst libraries.

Secondary screening is also schematically depicted in FIG. 4, whichdepicts a flow chart for data collection and processing in evaluatingcatalytic performance of catalysts according to the invention.Additional description of SMS tools in a combinatorial approach fordiscovering catalysts can be found in, e.g., Bergh, S. et al. Topics inCatalysts 23:1-4, 2003.

Thus, in accordance with various embodiments described herein,compositional and morphologically diverse catalysts can be rationallysynthesized to meet catalytic performance criteria. These and otheraspects of the present disclosure are described in more detail below.

DEFINITIONS

As used herein, and unless the context dictates otherwise, the followingterms have the meanings as specified below.

“Catalyst” means a substance which alters the rate of a chemicalreaction. A catalyst may either increase the chemical reaction rate(i.e. a “positive catalyst”) or decrease the reaction rate (i.e. a“negative catalyst”). Catalysts participate in a reaction in a cyclicfashion such that the catalyst is cyclically regenerated. “Catalytic”means having the properties of a catalyst.

“Salt” means a compound comprising negative and positive ions. Salts aregenerally comprised of metallic cations and non-metallic counter ions.As used herein, a metal salt is typically a source of the metal elementin a metal oxide catalyst.

“Crystal domain” means a continuous region over which a substance iscrystalline.

“Turnover number” is a measure of the number of reactant molecules acatalyst can convert to product molecules per unit time.

“Active” or “catalytically active” refers to a catalyst which hassubstantial activity in the reaction of interest. For example, in someembodiments a catalyst which is OCM active (i.e., has activity in theOCM reaction) has a C2 selectivity of 5% or more and/or a methaneconversion of 5% or more when the catalyst is employed as a heterogenouscatalyst in the oxidative coupling of methane at a temperature of 750°C. or less.

“Inactive” or “catalytically inactive” refers to a catalyst which doesnot have substantial activity in the reaction of interest. For example,in some embodiments a catalyst which is OCM inactive has a C2selectivity of less than 5% and/or a methane conversion of less than 5%when the catalyst is employed as a heterogenous catalyst in theoxidative coupling of methane at a temperature of 750° C. or less.

“Activation temperature” refers to the temperature at which a catalystbecomes catalytically active.

“OCM activity” refers to the ability of a catalyst to catalyse the OCMreaction.

A catalyst having “high OCM activity” refers to a catalyst having a C2selectivity of 50% or more and/or a methane conversion of 20% or morewhen the catalyst is employed as a heterogenous catalyst in theoxidative coupling of methane at a specific temperature, for example750° C. or less.

A catalyst having “moderate OCM activity” refers to a catalyst having aC2 selectivity of about 20-50% and/or a methane conversion of about10-20% or more when the catalyst is employed as a heterogenous catalystin the oxidative coupling of methane at a temperature of 750° C. orless.

A catalyst having “low OCM activity” refers to a catalyst having a C2selectivity of about 5-20% and/or a methane conversion of about 5-10% ormore when the catalyst is employed as a heterogenous catalyst in theoxidative coupling of methane at a temperature of 750° C. or less.

“Base material” refers to the major component of a catalyst. For examplea mixed oxide of manganese and magnesium which is doped with lithiumand/or boron comprises a manganese/magnesium oxide base material.

“Dopant” or “doping agent” or “doping element” is chemical compoundwhich is added to or incorporated within a catalyst base material tooptimize catalytic performance (e.g. increase or decrease catalyticactivity). As compared to the undoped catalyst, a doped catalyst mayincrease or decrease the selectivity, conversion, and/or yield of areaction catalyzed by the catalyst. Dopants which increase catalysticactivity are referred to as “promoters” while dopants which decreasecatalytic activity are referred to as “poisons”. The dopant may bepresent in the catalyst in any form and may be derived from any suitablesource of the element (e.g., chlorides, bromides, iodides, nitrates,oxynitrates, oxyhalides, acetates, formates, hydroxides, carbonates,phosphates, sulfates, alkoxides, and the like.)

“Atomic percent” (at % or at/at) or “atomic ratio” when used in thecontext of catalyst dopants refers to the ratio of the total number ofdopant atoms to the total number of non-oxygen atoms in the basematerial. For example, the atomic percent of dopant in a lithium dopedMg₆MnO₈ catalyst is determined by calculating the total number oflithium atoms and dividing by the sum of the total number of magnesiumand manganese atoms and multiplying by 100 (i.e., atomic percent ofdopant=[Li atoms/(Mg atoms+Mn atoms)]×100).

“Weight percent” (wt/wt) “when used in the context of catalyst dopantsrefers to the ratio of the total weight of dopant to the total combinedweight of the dopant and the catalyst. For example, the weight percentof dopant in a lithium doped Mg₆MnO₈ catalyst is determined bycalculating the total weight of lithium and dividing by the sum of thetotal combined weight of lithium and Mg₆MnO₈ and multiplying by 100(i.e., weight percent of dopant=[Li weight/(Li weight+Mg₆MnO₈weight)]×100).

“Group 1” elements include lithium (Li), sodium (Na), potassium (K),rubidium (Rb), cesium (Cs), and francium (Fr).

“Group 2” elements include beryllium (Be), magnesium (Mg), calcium (Ca),strontium (Sr), barium (Ba), and radium (Ra).

“Group 3” elements include scandium (Sc) and yttrium (Y).

“Group 4” elements include titanium (Ti), zirconium (Zr), hafnium (Hf),and rutherfordium (Rf).

“Group 5” elements include vanadium (V), niobium (Nb), tantalum (Ta),and dubnium (Db).

“Group 6” elements include chromium (Cr), molybdenum (Mo), tungsten (W),and seaborgium (Sg).

“Group 7” elements include manganese (Mn), technetium (Tc), rhenium(Re), and bohrium (Bh).

“Group 8” elements include iron (Fe), ruthenium (Ru), osmium (Os), andhassium (Hs).

“Group 9” elements include cobalt (Co), rhodium (Rh), iridium (Ir), andmeitnerium (Mt).

“Group 10” elements include nickel (Ni), palladium (Pd), platinum (Pt)and darmistadium (Ds).

“Group 11” elements include copper (Cu), silver (Ag), gold (Au), androentgenium (Rg).

“Group 12” elements include zinc (Zn), cadmium (Cd), mercury (Hg), andcopernicium (Cn).

“Group 16” elements include oxygen (O), sulfur (S), selenium (Se),tellurium (Te) and polonium (Po).

“Lanthanides” include lanthanum (La), cerium (Ce), praseodymium (Pr),neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu),gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium(Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

“Actinides” include actinium (Ac), thorium (Th), protactinium (Pa),uranium (U), neptunium (Np), plutonium (Pu), americium (Am), curium(Cm), berklelium (Bk), californium (Cf), einsteinium (Es), fermium (Fm),mendelevium (Md), nobelium (No), and lawrencium (Lr).

“Rare earth elements” include the lanthanides, actinides and Group 3.

“Metal element” or “metal” is any element, except hydrogen, selectedfrom Groups 1 through 12, lanthanides, actinides, aluminum (Al), gallium(Ga), indium (In), tin (Sn), thallium (Tl), lead (Pb), and bismuth (Bi).Metal elements include metal elements in their elemental form as well asmetal elements in an oxidized or reduced state, for example, when ametal element is combined with other elements in the form of compoundscomprising metal elements. For example, metal elements can be in theform of hydrates, salts, oxides, as well as various polymorphs thereof,and the like.

“Semi-metal element” refers to an element selected from boron (B),silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium(Te), and polonium (Po).

“Non-metal element” refers to an element selected from carbon (C),nitrogen (N), oxygen (O), fluorine (F), phosphorus (P), sulfur (S),chlorine (Cl), selenium (Se), bromine (Br), iodine (I), and astatine(At).

“Conversion” means the mole fraction (i.e., percent) of a reactantconverted to a product or products.

“Selectivity” refers to the percent of converted reactant that went to aspecified product, e.g., C2 selectivity is the % of converted methanethat formed ethane and ethylene, C3 selectivity is the % of convertedmethane that formed propane and propylene, CO selectivity is the % ofconverted methane that formed CO.

“Yield” is a measure of (e.g. percent) of product obtained relative tothe theoretical maximum product obtainable. Yield is calculated bydividing the amount of the obtained product in moles by the theoreticalyield in moles. Percent yield is calculated by multiplying this value by100. C2 yield is defined as the sum of the ethane and ethylene molarflow at the reactor outlet multiplied by two and divided by the inletmethane molar flow. C3 yield is defined as the sum of propane andpropylene molar flow at the reactor outlet multiplied by three anddivided by the inlet methane molar flow. C2+ yield is the sum of the C2yield and C3 yield. Yield is also calculable by multiplying the methaneconversion by the relevant selectivity, e.g. C2 yield is equal to themethane conversion times the C2 selectivity.

“C2” yield is the total combined yield of ethane and ethylene.

“C2” selectivity is the combined selectivity for ethane and ethylene.

“Bulk catalyst” or “bulk material” means a catalyst prepared bytraditional techniques, for example by milling or grinding largecatalyst particles to obtain smaller/higher surface area catalystparticles.

“Nanostructured catalyst” means a catalyst having at least one dimensionon the order of nanometers (e.g. between about 1 and 100 nanometers).Non-limiting examples of nanostructured catalysts include nanoparticlecatalysts and nanowire catalysts.

“Nanoparticle” means a particle having at least one diameter on theorder of nanometers (e.g. between about 1 and 100 nanometers).

“Nanowire” means a nanowire structure having at least one diameter onthe order of nanometers (e.g. between about 1 and 100 nanometers) and anaspect ratio greater than 10:1. The “aspect ratio” of a nanowire is theratio of the actual length (L) of the nanowire to the diameter (D) ofthe nanowire. Aspect ratio is expressed as L:D. Exemplary nanowires areknown in the art and described in more detail in co-pending U.S.application Ser. No. 13/115,082 (U.S. Pub. No. 2012/0041246); U.S.Provisional Application Nos. 61/564,834 and 61/564,836; and U.S.Provisional Application entitled “Nanowire Catalysts”, filed May 24,2012, the full disclosures of which are hereby incorporated by referencein their entirety for all purposes.

An “extrudate” refers to a material (e.g., catalytic material) preparedby forcing a semisolid material comprising a catalyst through a die oropening of appropriate shape. Extrudates can be prepared in a variety ofshapes and structures by common means known in the art.

A “pellet” or “pressed pellet” refers to a material (e.g., catalyticmaterial) prepared by applying pressure to (i.e., compressing) amaterial comprising a catalyst into a desired shape. Pellets havingvarious dimensions and shapes can be prepared according to commontechniques in the art.

“Monolith” or “monolith support” is generally a structure formed from asingle structural unit preferably having passages disposed through it ineither an irregular or regular pattern with porous or non-porous wallsseparating adjacent passages. Examples of such monolithic supportsinclude, e.g., ceramic or metal foam-like or porous structures. Thesingle structural unit may be used in place of or in addition toconventional particulate or granular catalysts (e.g., pellets orextrudates). Examples of such irregular patterned monolith substratesinclude filters used for molten metals. Monoliths generally have aporous fraction ranging from about 60% to 90% and a flow resistancesubstantially less than the flow resistance of a packed bed of similarvolume (e.g., about 10% to 30% of the flow resistance of a packed bed ofsimilar volume). Examples of regular patterned substrates includemonolith honeycomb supports used for purifying exhausts from motorvehicles and used in various chemical processes and ceramic foamstructures having irregular passages. Many types of monolith supportstructures made from conventional refractory or ceramic materials suchas alumina, zirconia, yttria, silicon carbide, and mixtures thereof, arewell known and commercially available from, among others, Corning, lac.;Vesuvius Hi-Tech Ceramics, Inc.; and Porvair Advanced Materials, Inc.and SiCAT (Sicatalyst.com). Monoliths include foams, honeycombs, foils,mesh, guaze and the like.

“Alkane” means a straight chain or branched, noncyclic or cyclic,saturated aliphatic hydrocarbon. Alkanes include linear, branched andcyclic structures. Representative straight chain alkanes includemethane, ethane, n-propane, n-butane, n-pentane, n-hexane, and the like;while branched alkanes include isopropane, sec-butane, isobutane,tert-butane, isopentane, and the like. Representative cyclic alkanesinclude cyclopropane, cyclobutane, cyclopentane, cyclohexane, and thelike. “Alkene” means a straight chain or branched, noncyclic or cyclic,unsaturated aliphatic hydrocarbon having at least one carbon-carbondouble bond. Alkenes include linear, branched and cyclic structures.Representative straight chain and branched alkenes include ethylene,propylene, 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene,3-methyl-1-butene, 2-methyl-2-butene, 2,3-dimethyl-2-butene, and thelike. Cyclic alkenes include cyclohexene and cyclopentene and the like.“Alkyne” means a straight chain or branched, noncyclic or cyclic,unsaturated aliphatic hydrocarbon having at least one carbon-carbontriple bond. Alkynes include linear, branched and cyclic structures.Representative straight chain and branched alkynes include acetylene,propyne, 1-butyne, 2-butyne, 1-pentyne, 2-pentyne, 3-methyl-1-butyne,and the like. Representative cyclic alkynes include cycloheptyne and thelike.

“Aromatic” means a carbocyclic moiety having a cyclic system ofconjugated p orbitals. Representative examples of aromatics includebenzene, naphthalene and toluene.

“Carbon-containing compounds” are compounds which comprise carbon.Non-limiting examples of carbon-containing compounds includehydrocarbons, CO and CO₂.

“Oxide” refers to a metal compound comprising oxygen. Examples of oxidesinclude, but are not limited to, metal oxides (M_(x)O_(y)), metaloxyhalide (M_(x)O_(y)X_(z)), metal oxynitrates (M_(x)O_(y)(NO₃)_(x)),metal phosphates (M_(x)(PO₄)_(y)), and the like, wherein x, y and z arenumbers from 1 to 100.

“Mixed oxide” or “mixed metal oxide” refers to a compound comprising twoor more oxidized metals and oxygen (i.e., M1_(x)M2_(y)O_(z), wherein M1and M2 are the same or different metal elements, 0 is oxygen and x, yand z are numbers from 1 to 100). A mixed oxide may comprise metalelements in various oxidation states and may comprise more than one typeof metal element. For example, a mixed oxide of manganese and magnesiumcomprises oxidized forms of magnesium and manganese. Each individualmanganese and magnesium atom may or may not have the same oxidationstate. Mixed oxides comprising 2, 3, 4, 5, 6 or more metal elements canbe represented in an analogous manner. Mixed oxides also includeoxy-hydroxides (e.g., M_(x)O_(y)OH_(z), wherein M is a metal element, Ois oxygen, x, y and z are numbers from 1 to 100 and OH is hydroxy).Mixed oxides may be represented herein as M1-M2, wherein M1 and M2 areeach independently a metal element.

“Rare earth oxide” refers to an oxide of an element from group 3,lanthanides or actinides. Rare earth oxides include mixed oxidecontaining a rare earth element. Examples of rare earth oxides include,but are not limited to, La₂O₃, Nd₂O₃, Yb₂O₃, Eu₂O₃, Sm₂O₃, Y₂O₃, Ce₂O₃,Pr₂O₃, Ln1_(4-x)Ln2_(x)O₆, La_(4-x)Ln1_(x)O₆, La_(4-x)Nd_(x)O₆, whereinLn1 and Ln2 are each independently a lanthanide element, wherein Ln1 andLn2 are not the same and x is a number ranging from greater than 0 toless than 4, La₃NdO₆, LaNd₃O₆, La_(1.5)Nd_(2.5)O₆, La_(2.5)Nd_(1.5)O₆,La_(3.2)Nd_(0.8)O₆, La_(3.5)Nd_(0.5)O₆, La_(3.8)Nd_(0.2)O₆, Y—La, Zr—La,Pr—La and Ce—La.

Catalysts

1. Molecular Composition of the Catalysts

As noted above, disclosed herein are catalysts useful in variouscatalytic reactions. In some embodiments, the catalysts are bulkcatalysts (i.e., not nanowire or other nanostructured catalysts). Insome embodiments, the catalysts comprise one or more metal elements forexample, the catalysts may be mono-metallic, bi-metallic, tri-metallic,etc (i.e. contain one, two, three, etc. metal elements). In someembodiments, the metal elements are present in the catalysts inelemental form while in other embodiments the metal elements are presentin oxidized form. In other embodiments the metal elements are present inthe catalysts in the form of a compound comprising a metal element. Themetal element or compound comprising the metal element may be in theform of oxides (e.g., mixed oxides), hydroxides, carbonates,oxy-hydroxides, oxycarbonates, salts, hydrates, and the like. The metalelement or compound comprising the metal element may also be in the formof any of a number of different polymorphs or crystal structures.

In other embodiments, the catalysts may comprise one or more elementfrom group 2 and one or more element from group 7 which may be in theform of an oxide. For example, the catyst may comprise magnesium andmanganese. The magnesium and manganese may be in oxidized form, forexample in the form of a mixed metal oxide.

Catalysts comprising mixed oxides of Mn and Mg are well suited forincorporation of dopants because magnesium atoms can be easilysubstituted by other atoms as long as their size is comparable withmagnesium. A family of “doped” Mg₆MnO₈ compounds with the compositionM_((x))Mg_((6-x))MnO₈, wherein each M is independently a dopant asdefined herein and x is 0 to 6, can thus be created. The oxidation stateof Mn can be tuned by selecting different amounts (i.e., differentvalues of x) of M with different oxidation states, for exampleLi_((x))Mg_((6-x))MnO₈ would contain a mixture of Mn(IV) and Mn(V) withx<1 and a mixture that may include Mn(V), Mn(VI), Mn(VII) with x>1. Themaximum value of x depends on the ability of a particular atom M to beincorporated in the Mg₆MnO₈ crystal structure and therefore variesdepending on M. It is believed that the ability to tune the manganeseoxidation state as described above could have advantageous effect on thecatalytic activity (e.g., selectivity, yield, conversion, etc.) of thedisclosed catalysts in various reactions, including the OCM reaction.Accordingly, in some embodiments, the present disclosure provides amixed oxide of manganese and magnesium which has been doped with lithiumand boron. In further embodiments, the catalyst comprises a C₂selectivity of greater than 50% and a methane conversion of greater than20% when the catalyst is employed as a heterogenous catalyst in theoxidative coupling of methane at a temperature of 750° C. or less.

Suprisingly, it has been found that addition of further dopants to theabove described catalyst increases the catalytic activity of thecatalyst in the OCM and other reactions. For example, a catalystcomprising a mixed oxide of manganese and magnesium which furthercomprises lithium and boron and at least one doping element from any ofgroups 1-13 are effective catalysts for use in the OCM reaction. In somespecific examples, the at least one doping element is from groups 4, 9,12 or 13, and in further embodiments, the catalyst comprises a C₂selectivity of greater than 50% and a methane conversion of greater than20% when the catalyst is employed as a heterogenous catalyst in theoxidative coupling of methane at a temperature of 750° C. or less. Insome examples, the doping element is rhodium. In other examples, thedoping element is cobalt. In yet other embodiments, the doping elementis zirconium, while in other embodiments, the doping element is zinc.Other embodiments include a gallium doping element or a sodium dopingelement.

In addition, Applicants have discovered that further doping of themanganese/magnesium mixed oxide catalyst can further improve thecatalytic activity of the catalyst. For example, although sodium itselfis not a promoting dopant, it has been found that addition of sodium,together with a cobalt or gallium dopant to the above catalyst resultsin an effective OCM catalyst. Thus in one embodiment of the foregoing,the present disclosure provides a mixed oxide of manganese and magnesiumwhich further includes lithium, boron, cobalt and sodium as dopants. Inother examples, the catalyst comprises a mixed oxide of manganese andmagnesium which further includes lithium, boron, gallium and sodium asdopants.

Inclusion of even further dopants within the above noted catalysts canimprove the activity thereof. For example, in some embodiments thecatalyst comprises a mixed oxide of manganese and magnesium and furthercomprises lithium and boron dopants and at least one doping element fromgroups 4, 9, 12, 13 or combinations thereof, and further comprises atleast one additional doping element from group 2. For example, acatalyst comprising a mixed oxide of manganese and magnesium whichfurther includes lithium, boron, cobalt and sodium can be further dopedwith beryllium, barium, aluminum, hafnium or combinations thereof. Inother embodiments, the mixed oxide of manganese and magnesium is furtherdoped with beryllium. In other embodiments, the mixed oxide of manganeseand magnesium is further doped with barium. In other embodiments, themixed oxide of manganese and magnesium is further doped with aluminum.In other embodiments, the mixed oxide of manganese and magnesium isfurther doped with hafnium.

Similarly, a catalyst comprising a mixed oxide of manganese andmagnesium which further includes lithium, boron, gallium and sodium canbe further doped with beryllium, barium, aluminum, hafnium orcombinations thereof. In other embodiments of the foregoing catalyst,the mixed oxide of manganese and magnesium is further doped withberyllium. In other embodiments, the mixed oxide of manganese andmagnesium is further doped with barium. In other embodiments, the mixedoxide of manganese and magnesium is further doped with aluminum. Inother embodiments, the mixed oxide of manganese and magnesium is furtherdoped with hafnium.

Mixed oxides comprising manganese, tungsten and sodium (Na/Mn/W/O) is apromising OCM catalyst. The Na/Mn/W/O system is attractive due to itshigh C2 selectivity and yield. Unfortunately, good catalytic activity isonly achievable at temperatures greater than 800° C. and although theexact active portion of the catalyst is still subject to debate, it isthought that sodium plays an important role in the catalytic cycle. Inaddition, the Na/Mn/W/O catalyst surface area is relatively low <2 m²/g.However, applicants have discovered that addition of certain dopants tothe Na/Mn/W/O catalyst system can increase the catalytic activitythereof. In addition, certain catalyst supports as described below, withor without dopants, can increase the catalytic activity of the Na/Mn/W/Ocatalyst, for example in the OCM reaction. In some embodiments, theNa/Mn/W/O catalyst comprises a C₂ selectivity of greater than 50% and amethane conversion of greater than 20% when the catalyst is employed asa heterogenous catalyst in the oxidative coupling of methane at atemperature of 750° C. or less.

Doping elements which have been found to increase the catalytic activityof a Na/Mn/W/O catalyst include elements from groups 2, 16 orcombinations thereof. Accordingly, in some embodiments the Na/Mn/W/Ocatalyst is doped with at least one doping element from group 2, 16 orcombinations thereof. For example, some embodiments include beryllium,barium, aluminum, hafnium or combinations thereof as dopants. In otherembodiments, the doping element is beryllium. In some other embodiments,the doping element is barium. In yet other embodiments, the dopingelement is aluminum, while in other embodiments, the doping element ishafnium. The Na/Mn/W/O catalyst (doped or undoped) has also been foundto benefit from various catalyst supports, including those describedbelow. For example, in some embodiments the catalyst support is SiO₂. Inother embodiments, the catalyst support is SiO₂, ZrO₂, HfO₂, InO₂ orcombinations thereof.

Catalysts comprising rare earth oxides (i.e., lanthanides, actinides andGroup 3) doped with various elements are also effective catalysts in theOCM reaction. In some embodiments the rare earth oxide is a rare earthmixed oxide (i.e., an oxide of two or more rare earth elements). Therare earth oxide may comprise any rare earth element, and in cetainembodiments the rare earth element is La, Nd, Eu, Sm, Yb, Gd or Y. Insome embodiments, the rare earth element is La. In other embodiments,the rare earth element is Nd. In other embodiments, the rare earthelement is Eu. In other embodiments, the rare earth element is Sm. Inother embodiments, the rare earth element is Yb. In other embodiments,the rare earth element is Gd. In other embodiments, the rare earthelement is Y.

In certain embodiments of the catalysts comprising rare earth oxides,the catalyst may further comprise a dopant selected from alkaline earth(Group 2) elements. For example, in some embodiments the dopant isselected from Be, Mg, Ca, Sr and Ba. In other embodiments, the dopant isBe. In other embodiments, the dopant is Ca. In other embodiments, thedopant is Sr. In other embodiments, the dopant is Ba.

In some specific embodiments, the rare earth oxide is a mixed rare earthoxide such as La₃NdO₆, LaNd₃O₆, La_(1.5)Nd_(2.5)O₆, La_(2.5)Nd_(1.5)O₆,La_(3.2)Nd_(0.8)O₆, La_(3.5)Nd_(0.5)O₆, La_(3.8)Nd_(0.2)O₆ orcombinations thereof and the like.

The degree of effectiveness of a particular dopant is a function of therare earth used and the concentration of the dopant. In addition toAlkali earth elements, further embodiments of the rare earth oxidecatalysts include embodiments wherein the catalysts comprise alkalielements as dopants which further promote the selectivity of the OCMcatalytic activity of the doped material. In yet other embodiments ofthe foregoing, the catalysts comprise both an alkali element and alkaliearth element as dopant.

In still further embodiments, the catalyst comprises a rare earth oxide(e.g., rare earth mixed oxies) and at least one dopant is selected fromgroups 1-16, lanthanides actinides or combinations thereof. In certainembodiments, such catalysts comprises a C₂ selectivity of greater than50% and a methane conversion of greater than 20% when the catalyst isemployed as a heterogenous catalyst in the oxidative coupling of methaneat a temperature of 750° C. or less. In some embodiments, the at leastone doping element is selected from groups 1-4, 8, 13, 14, lactinides,actinides and combinations thereof. In some other embodiments, the atleast one doping element is selected from groups 1-6, 8, 11, 13-15,lactinides, actinides and combinations thereof.

In some further embodiments of the foregoing, the at least one dopingelement is a rare earth element. In some embodiments, the at least onedoping element is Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd,Hf, Ho, Tm, W, La, K, Dy, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi,Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn,Ir, As, Li, Tb, Er, Te or Mo.

In other embodiments, the at least one doping element is sodium. Inother embodiments, the at least one doping element is magnesium. Inother embodiments, the at least one doping element is calcium. In otherembodiments, the at least one doping element is strontium. In otherembodiments, the at least one doping element is gallium. In otherembodiments, the at least one doping element is Scandium. In otherembodiments, the at least one doping element is yttrium. In otherembodiments, the at least one doping element is zirconium. In otherembodiments, the at least one doping element is indium. In otherembodiments, the at least one doping element is neodiumium. In otherembodiments, the at least one doping element is europium. In otherembodiments, the at least one doping element is cerium. In otherembodiments, the at least one doping element is gadolinium. In otherembodiments, the at least one doping element is hafnium. In otherembodiments, the at least one doping element is holmium. In otherembodiments, the at least one doping element is thulium. In otherembodiments, the at least one doping element is tungsten. In otherembodiments, the at least one doping element is lanthanum. In otherembodiments, the at least one doping element is potassium. In otherembodiments, the at least one doping element is dysprosium. In otherembodiments, the at least one doping element is caesium. In otherembodiments, the at least one doping element is sulfur. In otherembodiments, the at least one doping element is zinc. In otherembodiments, the at least one doping element is rubidium. In otherembodiments, the at least one doping element is barium. In otherembodiments, the at least one doping element is ytterbium. In otherembodiments, the at least one doping element is nickel. In otherembodiments, the at least one doping element is lutetium. In otherembodiments, the at least one doping element is tantalum. In otherembodiments, the at least one doping element is phosphorous. In otherembodiments, the at least one doping element is platinum. In otherembodiments, the at least one doping element is bismuth. In otherembodiments, the at least one doping element is tin. In otherembodiments, the at least one doping element is niobium. In otherembodiments, the at least one doping element is antimony. In otherembodiments, the at least one doping element is germanium. In otherembodiments, the at least one doping element is silver. In otherembodiments, the at least one doping element is gold. In otherembodiments, the at least one doping element is lead. In otherembodiments, the at least one doping element is rhenium. In otherembodiments, the at least one doping element is iron. In otherembodiments, the at least one doping element is aluminum. In otherembodiments, the at least one doping element is thallium. In otherembodiments, the at least one doping element is praseodymium. In otherembodiments, the at least one doping element is cobalt. In otherembodiments, the at least one doping element is rhodium. In otherembodiments, the at least one doping element is titanium. In otherembodiments, the at least one doping element is vanadium. In otherembodiments, the at least one doping element is chromium. In otherembodiments, the at least one doping element is manganese. In otherembodiments, the at least one doping element is iridium. In otherembodiments, the at least one doping element is arsenic. In otherembodiments, the at least one doping element is lithium. In otherembodiments, the at least one doping element is terbium. In otherembodiments, the at least one doping element is erbium. In otherembodiments, the at least one doping element is tellurium. In otherembodiments, the at least one doping element is molybdenum.

In some embodiments, the catalyst comprises a rare earth oxide and acombination of at least two different doping elements. For example, insome embodiments the two different doping elements are selected from Na,Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K,Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge,Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb,Er, Te and Mo. In other embodiments, the combination of at least twodoping elements is Eu/Na, Sr/Na, Mg/Na, Sr/W, K/La, K/Na, Li/Cs, Li/Na,Zn/K, Li/K, Rb/Hf, Ca/Cs, Hf/Bi, Sr/Sn, Sr/W, Sr/Nb, Zr/W, Y/W, Na/W,Bi/W, Bi/Cs, Bi/Ca, Bi/Sn, Bi/Sb, Ge/Hf, Hf/Sm, Sb/Ag, Sb/Bi, Sb/Au,Sb/Sm, Sb/Sr, Sb/W, Sb/Hf, Sb/Yb, Sb/Sn, Yb/Au, Yb/Ta, Yb/W, Yb/Sr,Yb/Pb, Yb/W, Yb/Ag, Au/Sr, W/Ge, Ta/Hf, W/Au, Ca/W, Au/Re, Sm/Li, La/K,Zn/Cs, Zr/Cs, Ca/Ce, Li/Sr, Cs/Zn, Dy/K, La/Mg, In/Sr, Sr/Cs, Ga/Cs,Lu/Fe, Sr/Tm, La/Dy, Mg/K, Zr/K, Li/Cs, Sm/Cs, In/K, Lu/Tl, Pr/Zn,Lu/Nb, Na/Pt, Na/Ce, Ba/Ta, Cu/Sn, Ag/Au, Al/Bi, Al/Mo, Al/Nb, Au/Pt,Ga/Bi, Mg/W, Pb/Au, Sn/Mg, Zn/Bi, Gd/Ho, Zr/Bi, Ho/Sr, Ca/Sr, Sr/Pb orSr/Hf.

In other embodiments, the combination of at least two different dopingelements is La/Nd, La/Sm, La/Ce, La/Sr, Eu/Na, Eu/Gd, Ca/Na, Eu/Sm,Eu/Sr, Mg/Sr, Ce/Mg, Gd/Sm, Sr/W, Sr/Ta, Au/Re, Au/Pb, Bi/Hf, Sr/Sn,Mg/N, Ca/S, Rb/S, Sr/Nd, Eu/Y, Mg/Nd, Sr/Na, Nd/Mg, La/Mg, Yb/S, Mg/Na,Sr/W, K/La, K/Na, Li/Cs, Li/Na, Zn/K, Li/K, Rb/Hf, Ca/Cs, Hf/Bi, Sr/Sn,Sr/W, Sr/Nb, Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca, Bi/Sn, Bi/Sb, Ge/Hf,Hf/Sm, Sb/Ag, Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W, Sb/Hf, Sb/Yb, Sb/Sn,Yb/Au, Yb/Ta, Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag, Au/Sr, W/Ge, Ta/Hf, W/Au,Ca/W, Au/Re, Sm/Li, La/K, Zn/Cs, Zr/Cs, Ca/Ce, Li/Sr, Cs/Zn, Dy/K,La/Mg, In/Sr, Sr/Cs, Ga/Cs, Lu/Fe, Sr/Tm, La/Dy, Mg/K, Zr/K, Li/Cs,Sm/Cs, In/K, Lu/Tl, Pr/Zn, Lu/Nb, Na/Pt, Na/Ce, Ba/Ta, Cu/Sn, Ag/Au,Al/Bi, Al/Mo, Al/Nb, Au/Pt, Ga/Bi, Mg/W, Pb/Au, Sn/Mg, Zn/Bi, Gd/Ho,Zr/Bi, Ho/Sr, Ca/Sr, Sr/Pb or Sr/Hf.

In other embodiments, the combination of two doping elements is La/Nd.In other embodiments, the combination of two doping elements is La/Sm.In other embodiments, the combination of two doping elements is La/Ce.In other embodiments, the combination of two doping elements is La/Sr.In other embodiments, the combination of two doping elements is Eu/Na.In other embodiments, the combination of two doping elements is Eu/Gd.In other embodiments, the combination of two doping elements is Ca/Na.In other embodiments, the combination of two doping elements is Eu/Sm.In other embodiments, the combination of two doping elements is Eu/Sr.In other embodiments, the combination of two doping elements is Mg/Sr.In other embodiments, the combination of two doping elements is Ce/Mg.In other embodiments, the combination of two doping elements is Gd/Sm.In other embodiments, the combination of two doping elements is Sr/W. Inother embodiments, the combination of two doping elements is Sr/Ta. Inother embodiments, the combination of two doping elements is Au/Re. Inother embodiments, the combination of two doping elements is Au/Pb. Inother embodiments, the combination of two doping elements is Bi/Hf. Inother embodiments, the combination of two doping elements is Sr/Sn. Inother embodiments, the combination of two doping elements is Mg/N. Inother embodiments, the combination of two doping elements is Ca/S. Inother embodiments, the combination of two doping elements is Rb/S. Inother embodiments, the combination of two doping elements is Sr/Nd. Inother embodiments, the combination of two doping elements is Eu/Y. Inother embodiments, the combination of two doping elements is Mg/Nd. Inother embodiments, the combination of two doping elements is Sr/Na. Inother embodiments, the combination of two doping elements is Nd/Mg. Inother embodiments, the combination of two doping elements is La/Mg. Inother embodiments, the combination of two doping elements is Yb/S. Inother embodiments, the combination of two doping elements is Mg/Na. Inother embodiments, the combination of two doping elements is Sr/W. Inother embodiments, the combination of two doping elements is K/La. Inother embodiments, the combination of two doping elements is K/Na. Inother embodiments, the combination of two doping elements is Li/Cs. Inother embodiments, the combination of two doping elements is Li/Na. Inother embodiments, the combination of two doping elements is Zn/K. Inother embodiments, the combination of two doping elements is Li/K. Inother embodiments, the combination of two doping elements is Rb/Hf. Inother embodiments, the combination of two doping elements is Ca/Cs. Inother embodiments, the combination of two doping elements is Hf/Bi. Inother embodiments, the combination of two doping elements is Sr/Sn. Inother embodiments, the combination of two doping elements is Sr/W. Inother embodiments, the combination of two doping elements is Sr/Nb. Inother embodiments, the combination of two doping elements is Zr/W. Inother embodiments, the combination of two doping elements is Y/W. Inother embodiments, the combination of two doping elements is Na/W. Inother embodiments, the combination of two doping elements is Bi/W. Inother embodiments, the combination of two doping elements is Bi/Cs. Inother embodiments, the combination of two doping elements is Bi/Ca. Inother embodiments, the combination of two doping elements is Bi/Sn. Inother embodiments, the combination of two doping elements is Bi/Sb. Inother embodiments, the combination of two doping elements is Ge/Hf. Inother embodiments, the combination of two doping elements is Hf/Sm. Inother embodiments, the combination of two doping elements is Sb/Ag. Inother embodiments, the combination of two doping elements is Sb/Bi. Inother embodiments, the combination of two doping elements is Sb/Au. Inother embodiments, the combination of two doping elements is Sb/Sm. Inother embodiments, the combination of two doping elements is Sb/Sr. Inother embodiments, the combination of two doping elements is Sb/W. Inother embodiments, the combination of two doping elements is Sb/Hf. Inother embodiments, the combination of two doping elements is Sb/Yb. Inother embodiments, the combination of two doping elements is Sb/Sn. Inother embodiments, the combination of two doping elements is Yb/Au. Inother embodiments, the combination of two doping elements is Yb/Ta. Inother embodiments, the combination of two doping elements is Yb/W. Inother embodiments, the combination of two doping elements is Yb/Sr. Inother embodiments, the combination of two doping elements is Yb/Pb. Inother embodiments, the combination of two doping elements is Yb/W. Inother embodiments, the combination of two doping elements is Yb/Ag. Inother embodiments, the combination of two doping elements is Au/Sr. Inother embodiments, the combination of two doping elements is W/Ge. Inother embodiments, the combination of two doping elements is Ta/Hf. Inother embodiments, the combination of two doping elements is W/Au. Inother embodiments, the combination of two doping elements is Ca/W. Inother embodiments, the combination of two doping elements is Au/Re. Inother embodiments, the combination of two doping elements is Sm/Li. Inother embodiments, the combination of two doping elements is La/K. Inother embodiments, the combination of two doping elements is Zn/Cs. Inother embodiments, the combination of two doping elements is Zr/Cs. Inother embodiments, the combination of two doping elements is Ca/Ce. Inother embodiments, the combination of two doping elements is Li/Sr. Inother embodiments, the combination of two doping elements is Cs/Zn. Inother embodiments, the combination of two doping elements is Dy/K. Inother embodiments, the combination of two doping elements is La/Mg. Inother embodiments, the combination of two doping elements is In/Sr. Inother embodiments, the combination of two doping elements is Sr/Cs. Inother embodiments, the combination of two doping elements is Ga/Cs. Inother embodiments, the combination of two doping elements is Lu/Fe. Inother embodiments, the combination of two doping elements is Sr/Tm. Inother embodiments, the combination of two doping elements is La/Dy. Inother embodiments, the combination of two doping elements is Mg/K. Inother embodiments, the combination of two doping elements is Zr/K. Inother embodiments, the combination of two doping elements is Li/Cs. Inother embodiments, the combination of two doping elements is Sm/Cs. Inother embodiments, the combination of two doping elements is In/K. Inother embodiments, the combination of two doping elements is Lu/Tl. Inother embodiments, the combination of two doping elements is Pr/Zn. Inother embodiments, the combination of two doping elements is Lu/Nb. Inother embodiments, the combination of two doping elements is Na/Pt. Inother embodiments, the combination of two doping elements is Na/Ce. Inother embodiments, the combination of two doping elements is Ba/Ta. Inother embodiments, the combination of two doping elements is Cu/Sn. Inother embodiments, the combination of two doping elements is Ag/Au. Inother embodiments, the combination of two doping elements is Al/Bi. Inother embodiments, the combination of two doping elements is Al/Mo. Inother embodiments, the combination of two doping elements is Al/Nb. Inother embodiments, the combination of two doping elements is Au/Pt. Inother embodiments, the combination of two doping elements is Ga/Bi. Inother embodiments, the combination of two doping elements is Mg/W. Inother embodiments, the combination of two doping elements is Pb/Au. Inother embodiments, the combination of two doping elements is Sn/Mg. Inother embodiments, the combination of two doping elements is Zn/Bi. Inother embodiments, the combination of two doping elements is Gd/Ho. Inother embodiments, the combination of two doping elements is Zr/Bi. Inother embodiments, the combination of two doping elements is Ho/Sr. Inother embodiments, the combination of two doping elements is Ca/Sr. Inother embodiments, the combination of two doping elements is Sr/Pb. Inother embodiments, the combination of two doping elements is Sr/Hf.

In some other embodiments, the oxide of a rare earth element comprises acombination of at least three different doping elements. In certainexamples, the three different doping elements are selected from Na, Mg,Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy,In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag,Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb, Er,Te and Mo. In certain other embodiments, the combination of at leastthree different doping elements is Mg/La/K, Na/Dy/K, Na/La/Dy, Na/La/Eu,Na/La/K, K/La/S, Li/Cs/La, Li/Sr/Cs, Li/Ga/Cs, Li/Na/Sr, Li/Sm/Cs,Cs/K/La, Sr/Cs/La, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Rb/Sr/Lu, Na/Eu/Hf,Dy/Rb/Gd, Na/Pt/Bi, Ca/Mg/Na, Na/K/Mg, Na/Li/Cs, La/Dy/K, Sm/Li/Sr,Li/Rb/Ga, Li/Cs/Tm, Li/K/La, Ce/Zr/La, Ca/Al/La, Sr/Zn/La, Cs/La/Na,La/S/Sr, Rb/Sr/La, Na/Sr/Lu, Sr/Eu/Dy, La/Dy/Gd, Gd/Li/K, Rb/K/Lu,Na/Ce/Co, Ba/Rh/Ta, Na/Al/Bi, Cs/Eu/S, Sm/Tm/Yb, Hf/Zr/Ta, Na/Ca/Lu,Gd/Ho/Sr, Ca/Sr/W, Na/Zr/Eu/Tm, Sr/W/Li, Ca/Sr/W or Mg/Nd/Fe.

In still other embodiments, the combination of at least three differentdoping elements is Nd/Sr/CaO, La/Nd/Sr, La/Bi/Sr, Mg/Nd/Fe, Mg/La/K,Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/K, K/La/S, Li/Cs/La, Li/Sr/Cs,Li/Ga/Cs, Li/Na/Sr, Li/Sm/Cs, Cs/K/La, Sr/Cs/La, Sr/Ho/Tm, La/Nd/S,Li/Rb/Ca, Rb/Sr/Lu, Na/Eu/Hf, Dy/Rb/Gd, Na/Pt/Bi, Ca/Mg/Na, Na/K/Mg,Na/Li/Cs, La/Dy/K, Sm/Li/Sr, Li/Rb/Ga, Li/Cs/Tm, Li/K/La, Ce/Zr/La,Ca/Al/La, Sr/Zn/La, Cs/La/Na, La/S/Sr, Rb/Sr/La, Na/Sr/Lu, Sr/Eu/Dy,La/Dy/Gd, Gd/Li/K, Rb/K/Lu, Na/Ce/Co, Ba/Rh/Ta, Na/Al/Bi, Cs/Eu/S,Sm/Tm/Yb, Hf/Zr/Ta, Na/Ca/Lu, Gd/Ho/Sr, Ca/Sr/W, Na/Zr/Eu/Tm, Sr/W/Li orCa/Sr/W.

In other embodiments, the combination of at least three different dopingelements is Nd/Sr/CaO. In other embodiments, the combination of at leastthree different doping elements is La/Nd/Sr. In other embodiments, thecombination of at least three different doping elements is La/Bi/Sr. Inother embodiments, the combination of at least three different dopingelements is Mg/Nd/Fe. In other embodiments, the combination of at leastthree different doping elements is Mg/La/K. In other embodiments, thecombination of at least three different doping elements is Na/Dy/K. Inother embodiments, the combination of at least three different dopingelements is Na/La/Dy. In other embodiments, the combination of at leastthree different doping elements is Na/La/Eu. In other embodiments, thecombination of at least three different doping elements is Na/La/K. Inother embodiments, the combination of at least three different dopingelements is K/La/S. In other embodiments, the combination of at leastthree different doping elements is Li/Cs/La. In other embodiments, thecombination of at least three different doping elements is Li/Sr/Cs. Inother embodiments, the combination of at least three different dopingelements is Li/Ga/Cs. In other embodiments, the combination of at leastthree different doping elements is Li/Na/Sr. In other embodiments, thecombination of at least three different doping elements is Li/Sm/Cs. Inother embodiments, the combination of at least three different dopingelements is Cs/K/La. In other embodiments, the combination of at leastthree different doping elements is Sr/Cs/La. In other embodiments, thecombination of at least three different doping elements is Sr/Ho/Tm. Inother embodiments, the combination of at least three different dopingelements is La/Nd/S. In other embodiments, the combination of at leastthree different doping elements is Li/Rb/Ca. In other embodiments, thecombination of at least three different doping elements is Rb/Sr/Lu. Inother embodiments, the combination of at least three different dopingelements is Na/Eu/Hf. In other embodiments, the combination of at leastthree different doping elements is Dy/Rb/Gd. In other embodiments, thecombination of at least three different doping elements is Na/Pt/Bi. Inother embodiments, the combination of at least three different dopingelements is Ca/Mg/Na. In other embodiments, the combination of at leastthree different doping elements is Na/K/Mg. In other embodiments, thecombination of at least three different doping elements is Na/Li/Cs. Inother embodiments, the combination of at least three different dopingelements is La/Dy/K. In other embodiments, the combination of at leastthree different doping elements is Sm/Li/Sr. In other embodiments, thecombination of at least three different doping elements is Li/Rb/Ga. Inother embodiments, the combination of at least three different dopingelements is Li/Cs/Tm. In other embodiments, the combination of at leastthree different doping elements is Li/K/La. In other embodiments, thecombination of at least three different doping elements is Ce/Zr/La. Inother embodiments, the combination of at least three different dopingelements is Ca/Al/La. In other embodiments, the combination of at leastthree different doping elements is Sr/Zn/La. In other embodiments, thecombination of at least three different doping elements is Cs/La/Na. Inother embodiments, the combination of at least three different dopingelements is La/S/Sr. In other embodiments, the combination of at leastthree different doping elements is Rb/Sr/La. In other embodiments, thecombination of at least three different doping elements is Na/Sr/Lu. Inother embodiments, the combination of at least three different dopingelements is Sr/Eu/Dy. In other embodiments, the combination of at leastthree different doping elements is La/Dy/Gd. In other embodiments, thecombination of at least three different doping elements is Gd/Li/K. Inother embodiments, the combination of at least three different dopingelements is Rb/K/Lu. In other embodiments, the combination of at leastthree different doping elements is Na/Ce/Co. In other embodiments, thecombination of at least three different doping elements is Ba/Rh/Ta. Inother embodiments, the combination of at least three different dopingelements is Na/Al/Bi. In other embodiments, the combination of at leastthree different doping elements is Cs/Eu/S. In other embodiments, thecombination of at least three different doping elements is Sm/Tm/Yb. Inother embodiments, the combination of at least three different dopingelements is Hf/Zr/Ta. In other embodiments, the combination of at leastthree different doping elements is Na/Ca/Lu. In other embodiments, thecombination of at least three different doping elements is Gd/Ho/Sr. Inother embodiments, the combination of at least three different dopingelements is Ca/Sr/W. In other embodiments, the combination of at leastthree different doping elements is Na/Zr/Eu/Tm. In other embodiments,the combination of at least three different doping elements is Sr/W/Li.In other embodiments, the combination of at least three different dopingelements is Ca/Sr/W.

In yet other embodiments, the oxide of a rare earth element comprises acombination of at least four different doping elements. In someexamples, the four different doping elements are selected from Na, Mg,Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy,In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag,Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb, Er,Te and Mo. More specific examples include catalysts wherein thecombination of at least four different doping elements is Sr/Sm/Ho/Tm,Na/K/Mg/Tm, Na/La/Eu/In, Na/La/Li/Cs, Li/Cs/La/Tm, Li/Cs/Sr/Tm,Li/Sr/Zn/K, Li/Ga/Cs, Li/K/Sr/La, Li/Na/Rb/Ga, Li/Na/Sr/La, Ba/Sm/Yb/S,Ba/Tm/K/La, Ba/Tm/Zn/K, Cs/La/Tm/Na, Cs/Li/K/La, Sm/Li/Sr/Cs,Sr/Tm/Li/Cs, Zr/Cs/K/La, Rb/Ca/In/Ni, Tm/Lu/Ta/P, Rb/Ca/Dy/P,Mg/La/Yb/Zn, Na/Sr/Lu/Nb, Na/Nd/In/K, K/La/Zr/Ag, Ho/Cs/Li/La,K/La/Zr/Ag, Na/Sr/Eu/Ca, K/Cs/Sr/La, Na/Mg/Tl/P, Sr/La/Dy/S,Na/Ga/Gd/Al, Sm/Tm/Yb/Fe, Rb/Gd/Li/K, Gd/Ho/Al/P, Na/Zr/Eu/T,Sr/Ho/Tm/Na, Na/Zr/Eu/Ca, Rb/Ga/Tm/Cs or La/Bi/Ce/Nd/Sr.

In other embodiments, the combination of at least four different dopingelements is Sr/Sm/Ho/Tm. In other embodiments, the combination of atleast four different doping elements is Na/K/Mg/Tm. In otherembodiments, the combination of at least four different doping elementsis Na/La/Eu/In. In other embodiments, the combination of at least fourdifferent doping elements is Na/La/Li/Cs. In other embodiments, thecombination of at least four different doping elements is Li/Cs/La/Tm.In other embodiments, the combination of at least four different dopingelements is Li/Cs/Sr/Tm. In other embodiments, the combination of atleast four different doping elements is Li/Sr/Zn/K. In otherembodiments, the combination of at least four different doping elementsis Li/Ga/Cs. In other embodiments, the combination of at least fourdifferent doping elements is Li/K/Sr/La. In other embodiments, thecombination of at least four different doping elements is Li/Na/Rb/Ga.In other embodiments, the combination of at least four different dopingelements is Li/Na/Sr/La. In other embodiments, the combination of atleast four different doping elements is Ba/Sm/Yb/S. In otherembodiments, the combination of at least four different doping elementsis Ba/Tm/K/La. In other embodiments, the combination of at least fourdifferent doping elements is Ba/Tm/Zn/K. In other embodiments, thecombination of at least four different doping elements is Cs/La/Tm/Na.In other embodiments, the combination of at least four different dopingelements is Cs/Li/K/La. In other embodiments, the combination of atleast four different doping elements is Sm/Li/Sr/Cs. In otherembodiments, the combination of at least four different doping elementsis Sr/Tm/Li/Cs. In other embodiments, the combination of at least fourdifferent doping elements is Zr/Cs/K/La. In other embodiments, thecombination of at least four different doping elements is Rb/Ca/In/Ni.In other embodiments, the combination of at least four different dopingelements is Tm/Lu/Ta/P. In other embodiments, the combination of atleast four different doping elements is Rb/Ca/Dy/P. In otherembodiments, the combination of at least four different doping elementsis Mg/La/Yb/Zn. In other embodiments, the combination of at least fourdifferent doping elements is Na/Sr/Lu/Nb. In other embodiments, thecombination of at least four different doping elements is Na/Nd/In/K. Inother embodiments, the combination of at least four different dopingelements is K/La/Zr/Ag. In other embodiments, the combination of atleast four different doping elements is Ho/Cs/Li/La. In otherembodiments, the combination of at least four different doping elementsis K/La/Zr/Ag. In other embodiments, the combination of at least fourdifferent doping elements is Na/Sr/Eu/Ca. In other embodiments, thecombination of at least four different doping elements is K/Cs/Sr/La. Inother embodiments, the combination of at least four different dopingelements is Na/Mg/Tl/P. In other embodiments, the combination of atleast four different doping elements is Sr/La/Dy/S. In otherembodiments, the combination of at least four different doping elementsis Na/Ga/Gd/Al. In other embodiments, the combination of at least fourdifferent doping elements is Sm/Tm/Yb/Fe. In other embodiments, thecombination of at least four different doping elements is Rb/Gd/Li/K. Inother embodiments, the combination of at least four different dopingelements is Gd/Ho/Al/P. In other embodiments, the combination of atleast four different doping elements is Na/Zr/Eu/T. In otherembodiments, the combination of at least four different doping elementsis Sr/Ho/Tm/Na. In other embodiments, the combination of at least fourdifferent doping elements is Na/Zr/Eu/Ca. In other embodiments, thecombination of at least four different doping elements is Rb/Ga/Tm/Cs.In other embodiments, the combination of at least four different dopingelements is La/Bi/Ce/Nd/Sr.

In some embodiments, the oxide of a rare earth element is a mixed oxide.

In other embodiments, the oxide of a rare earth element comprises alanthanum oxide, a neodimium oxide, a ytterbium oxide, a europium oxide,a samarium oxide, a yttrium oxide, a cerium oxide or a praseodymiumoxide.

In yet other embodiments, the oxide of a rare earth element comprisesLn1_(4-x)Ln2_(x)O₆, wherein Ln1 and Ln2 are each independently alanthanide element, wherein Ln1 and Ln2 are not the same and x is anumber ranging from greater than 0 to less than 4. For example, in someembodiments the rare earth oxide comprises La_(4-x)Nd_(x)O₆, wherein xis a number ranging from greater than 0 to less than 4. In even furtherembodiments, the rare earth oxide comprises La₃NdO₆, LaNd₃O₆,La_(1.5)Nd_(2.5)O₆, La_(2.5)Nd_(1.5)O₆, La_(3.2)Nd_(0.8)O₆,La_(3.5)Nd_(0.5)O₆, La_(3.8)Nd_(0.2)O₆ or combinations thereof.

In yet other embodiments, the oxide of a rare earth element comprises amixed oxide. For example, in some embodiments the mixed oxide comprisesY—La, Zr—La, Pr—La, Ce—La or combinations thereof.

In some embodiments, the rare earth oxide catalyst comprises a C₂selectivity of greater than 50% and a methane conversion of greater than20% when the catalyst is employed as a heterogenous catalyst in theoxidative coupling of methane at a temperature of 750° C. or less.

In other embodiments, the catalysts comprise La₂O₃ or LaO_(y)(OH)_(x),wherein x and y are each independently an integer from 1 to 10 dopedwith Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd orcombinations thereof. In yet further embodiments, the La₂O₃ orLaO_(y)(OH)_(x) catalysts are doped with binary dopant combinations ofEu/Na; Eu/Gd; Ca/Na; Eu/Sm; Eu/Sr; Mg/Sr; Ce/Mg; Gd/Sm, Mg/Na, Mg/Y,Ga/Sr or Nd/Mg.

In other embodiments, the catalysts comprise Nd₂O₃ or NdO_(y)(OH)_(x),wherein x and y are each independently an integer from 1 to 10, dopedwith Sr, Ca, Rb, Li, Na or combinations thereof. In certain otherembodiments, the Nd₂O₃ or NdO_(y)(OH)_(x) catalysts are doped withbinary dopant combinations of Ca/Sr or Rb/Sr.

In still other examples of the doped catalysts, the catalysts compriseYb₂O₃ or YbO_(y)(OH)_(x), wherein x and y are each independently aninteger from 1 to 10, doped with Sr, Ca, Ba, Nd or combinations thereof.In certain other embodiments, the Yb₂O₃ or YbO_(y)(OH)_(x) OCM catalystsare doped with a binary combination of Sr/Nd.

Still other examples of doped catalysts, the catalysts comprise Eu₂O₃ orEuO_(y)(OH)_(x), wherein x and y are each independently an integer from1 to 10, doped with Sr, Ba, Sm or combinations thereof or a binarydopant combination of Sr/Na.

Examples of dopants for Sm₂O₃ or SmO_(y)(OH)_(x) catalysts, wherein xand y are each independently an integer from 1 to 10, include Sr, andexamples of dopants for Y₂O₃ or YO_(y)(OH)_(x) catalysts wherein x and yare each independently an integer from 1 to 10, comprise Ga, La, Nd orcombinations thereof. In certain other embodiments, the Y₂O₃ orYO_(y)(OH)_(x) catalysts comprise a binary dopant combination of Sr/Nd,Eu/Y or Mg/Nd or a tertiary dopant combination of Mg/Nd/Fe.

Rare earth mixed oxide catalysts which without doping have low OCMselectivity can be greatly improved by doping to reduce their combustionactivity. In particular, catalysts comprising CeO₂ and Pr₂O₃ tend tohave strong total oxidation activity for methane, however doping withadditional rare earth elements can significantly moderate the combustionactivity and improve the overall utility of the catalyst. Examples ofdopants which improve the selectivity of the catalysts, for example thePr₂O₃ or PrO_(y)(OH)_(x) catalysts, wherein x and y are eachindependently an integer from 1 to 10, comprise binary dopants of Nd/Mg,La/Mg or Yb/Sr.

In yet other embodiments of the rare earth oxide, the rare earth elementmay be in the form of a metal oxyhalide, a metal oxynitrate or a metalphosphate.

In still other embodiments, the present disclosure provides a catalystcomprising a mixed oxide of manganese and tungsten, wherein the catalystfurther comprises a sodium dopant and at least one doping element fromgroups 2, 4-6, 8-15, lanthanides or combinations thereof. The catalystmay comprise a C₂ selectivity of greater than 50% and a methaneconversion of greater than 20% when the catalyst is employed as aheterogenous catalyst in the oxidative coupling of methane at atemperature of 750° C. or less.

In further embodiments of the foregoing, the at least one doping elementis Fe, Co, Ce, Cu, Ni, Sr, Ga, Zr, Pb, Zn, Cr, Pt, Al, Nb, La, Ba, Bi,Sn, In, Ru, P or combinations thereof. In this regard, all binary andternary combinations of the foregoing dopants are contemplated. The atleast one doping element may be Fe. The at least one doping element maybe Co. The at least one doping element may be Ce. The at least onedoping element may be Cu. The at least one doping element may be Ni. Theat least one doping element may be Sr. The at least one doping elementmay be Ga. The at least one doping element may be Zr. The at least onedoping element may be Pb. The at least one doping element may be Zn. Theat least one doping element may be Cr. The at least one doping elementmay be Pt. The at least one doping element may be Al. The at least onedoping element may be Nb. The at least one doping element may be La. Theat least one doping element may be Ba. The at least one doping elementmay be Bi. The at least one doping element may be Sn. The at least onedoping element may be In. The at least one doping element may be Ru. Theat least one doping element may be P.

Applicants have also found that mixed oxides of lanthanides and tungstenare effective catalysts, for example in the OCM reaction. Accordingly,in one embodiment the disclosure provides a catalyst comprising a mixedoxide of a lanthanide and tungsten, wherein the catalyst furthercomprises a sodium dopant and at least one doping element from groups 2,4-15, lanthanides or combinations thereof. In further embodiments, thecatalyst comprises a C₂ selectivity of greater than 50% and a methaneconversion of greater than 20% when the catalyst is employed as aheterogenous catalyst in the oxidative coupling of methane at atemperature of 750° C. or less.

In other embodiments of the foregoing, the lanthanide is Ce, Pr, Nd, La,Eu, Sm or Y. In other embodiments, the at least one doping element isFe, Co, Mn, Cu, Ni, Sr, Ga, Zr, Pb, Zn, Cr, Pt, Al, Nb, La, Ba, Bi, Sn,In, Ru, P or combinations thereof. Binary and ternary combinations ofthe foregoing dopants are also contemplated. The at least one dopingelement may be Fe. The at least one doping element may be Co. The atleast one doping element may be Mn. The at least one doping element maybe Cu. The at least one doping element may be Ni. The at least onedoping element may be Sr. The at least one doping element may be Ga. Theat least one doping element may be Zr. The at least one doping elementmay be Pb. The at least one doping element may be Zn. The at least onedoping element may be Cr. The at least one doping element may be Pt. Theat least one doping element may be Al. The at least one doping elementmay be Nb. The at least one doping element may be La. The at least onedoping element may be Ba. The at least one doping element may be Bi. Theat least one doping element may be Sn. The at least one doping elementmay be In. The at least one doping element may be Ru. The at least onedoping element may be P.

In addition to the above compositions, the present inventors havedetermined that certain rare earth compositions are useful as catalystsin a number of reactions, for example the OCM reaction. In someembodiments, these lanthanide compositions comprise La₂O₃, Nd₂O₃, Yb₂O₃,Eu₂O₃, Sm₂O₃, Ln1_(4-x)Ln2_(x)O₆, La_(4-x)Ln1_(x)O₆, La_(4-x)Nd_(x)O₆,wherein Ln1 and Ln2 are each independently a lanthanide element, whereinLn1 and Ln2 are not the same and x is a number ranging from greater than0 to less than 4, La₃NdO₆, LaNd₃O₆, La_(1.5)Nd_(2.5)O₆,La_(2.5)Nd_(1.5)O₆, La_(3.2)Nd_(0.8)O₆, La_(3.5)Nd_(0.5)O₆,La_(3.8)Nd_(0.2)O₆, or combinations thereof. Certain lanthanide mixedoxides such as Y—La, Zr—La, Pr—La or Ce—La are also useful as catalystsin the OCM reaction. Further, Applicants have discovered that certaindoping combinations, when combined with the above lanthanidecompositions, serve to enhance the catalytic activity of the catalystsin certain catalytic reactions, for example OCM. The dopants may bepresent in various levels (e.g., w/w or at/at), and the catalysts may beprepared by any number of methods. Various aspects of the abovelanthanide catalysts are provided in the following paragraphs and inTables 1-4.

As noted above, certain combinations of dopants have been found usefulwhen combined with certain catalysts. In one embodiment, the catalystcomprises a rare earth oxide and two or more dopants, wherein thedopants are selected from Eu/Na, Sr/Na, Na/Zr/Eu/Ca, Mg/Na, Sr/Sm/Ho/Tm,Sr/W, Mg/La/K, Na/K/Mg/Tm, Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/Eu/In,Na/La/K, Na/La/Li/Cs, K/La, K/La/S, K/Na, Li/Cs, Li/Cs/La, Li/Cs/La/Tm,Li/Cs/Sr/Tm, Li/Sr/Cs, Li/Sr/Zn/K, Li/Ga/Cs, Li/K/Sr/La, Li/Na,Li/Na/Rb/Ga, Li/Na/Sr, Li/Na/Sr/La, Li/Sm/Cs, Ba/Sm/Yb/S, Ba/Tm/K/La,Ba/Tm/Zn/K, Cs/K/La, Cs/La/Tm/Na, Cs/Li/K/La, Sm/Li/Sr/Cs, Sr/Cs/La,Sr/Tm/Li/Cs, Zn/K, Zr/Cs/K/La, Rb/Ca/In/Ni, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca,Li/K, Tm/Lu/Ta/P, Rb/Ca/Dy/P, Mg/La/Yb/Zn, Rb/Sr/Lu, Na/Sr/Lu/Nb,Na/Eu/Hf, Dy/Rb/Gd, Na/Pt/Bi, Rb/Hf, Ca/Cs, Ca/Mg/Na, Hf/Bi, Sr/Sn,Sr/W, Sr/Nb, Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca, Bi/Sn, Bi/Sb, Ge/Hf,Hf/Sm, Sb/Ag, Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W, Sb/Hf, Sb/Yb, Sb/Sn,Yb/Au, Yb/Ta, Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag, Au/Sr, W/Ge, Ta/Hf, W/Au,Ca/W, Au/Re, Sm/Li, La/K, Zn/Cs, Na/K/Mg, Zr/Cs, Ca/Ce, Na/Li/Cs, Li/Sr,Cs/Zn, La/Dy/K, Dy/K, La/Mg, Na/Nd/In/K, In/Sr, Sr/Cs, Rb/Ga/Tm/Cs,Ga/Cs, K/La/Zr/Ag, Lu/Fe, Sr/Tm, La/Dy, Sm/Li/Sr, Mg/K, Li/Rb/Ga,Li/Cs/Tm, Zr/K, Li/Cs, Li/K/La, Ce/Zr/La, Ca/Al/La, Sr/Zn/La, Sr/Cs/Zn,Sm/Cs, In/K, Ho/Cs/Li/La, Cs/La/Na, La/S/Sr, K/La/Zr/Ag, Lu/Tl, Pr/Zn,Rb/Sr/La, Na/Sr/Eu/Ca, K/Cs/Sr/La, Na/Sr/Lu, Sr/Eu/Dy, Lu/Nb, La/Dy/Gd,Na/Mg/Tl/P, Na/Pt, Gd/Li/K, Rb/K/Lu, Sr/La/Dy/S, Na/Ce/Co, Na/Ce,Na/Ga/Gd/Al, Ba/Rh/Ta, Ba/Ta, Na/Al/Bi, Cs/Eu/S, Sm/Tm/Yb/Fe, Sm/Tm/Yb,Hf/Zr/Ta, Rb/Gd/Li/K, Gd/Ho/Al/P, Na/Ca/Lu, Cu/Sn, Ag/Au, Al/Bi, Al/Mo,Al/Nb, Au/Pt, Ga/Bi, Mg/W, Pb/Au, Sn/Mg, Zn/Bi, Gd/Ho, Zr/Bi, Ho/Sr,Gd/Ho/Sr, Ca/Sr, Ca/Sr/W, Na/Zr/Eu/Tm, Sr/Ho/Tm/Na, Sr/Pb, Sr/W/Li,Ca/Sr/W and Sr/Hf.

In other embodiments of the foregoing rare earth oxide, the dopant isselected from Cs/Eu/S, Sm/Tm/Yb/Fe, Sm/Tm/Yb, Hf/Zr/Ta, Rb/Gd/Li/K,Gd/Ho/Al/P, Na/Ca/Lu, Cu/Sn, Ag/Au, Al/Bi, Al/Mo, Al/Nb, Au/Pt, Ga/Bi,Mg/W, Pb/Au, Sn/Mg, Zn/Bi, Gd/Ho, Zr/Bi, Ho/Sr, Gd/Ho/Sr, Ca/Sr,Ca/Sr/W, Na/Zr/Eu/Tm, Sr/Ho/Tm/Na, Sr/Pb, Ca, Sr/W/Li, Ca/Sr/W, Sr/Hf,Eu/Na, Sr/Na, Na/Zr/Eu/Ca, Mg/Na, Sr/Sm/Ho/Tm, Sr/W, Mg/La/K,Na/K/Mg/Tm, Na/Dy/K, Na/La/Dy, Na/La/Eu, Na/La/Eu/In, Na/La/K,Na/La/Li/Cs, K/La, K/La/S, K/Na, Li/Cs, Li/Cs/La, Li/Cs/La/Tm,Li/Cs/Sr/Tm, Li/Sr/Cs, Li/Sr/Zn/K, Li/Ga/Cs, Li/K/Sr/La, Li/Na,Li/Na/Rb/Ga and Li/Na/Sr.

In still other embodiments of the rare earth oxide, the dopant isselected from Li/Na/Sr/La, Li/Sm/Cs, Ba/Sm/Yb/S, Ba/Tm/K/La, Ba/Tm/Zn/K,Cs/K/La, Cs/La/Tm/Na, Cs/Li/K/La, Sm/Li/Sr/Cs, Sr/Cs/La, Sr/Tm/Li/Cs,Zn/K, Zr/Cs/K/La, Rb/Ca/In/Ni, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Li/K,Tm/Lu/Ta/P, Rb/Ca/Dy/P, Mg/La/Yb/Zn, Rb/Sr/Lu, Na/Sr/Lu/Nb, Na/Eu/Hf,Dy/Rb/Gd, Na/Pt/Bi, Rb/Hf, Ga/Cs, K/La/Zr/Ag, Lu/Fe, Sr/Tm, La/Dy,Sm/Li/Sr, Mg/K, Li/Rb/Ga, Li/Cs/Tm, Zr/K, Li/Cs, Li/K/La, Ce/Zr/La,Ca/Al/La, Sr/Zn/La, Sr/Cs/Zn, Sm/Cs, In/K, Ho/Cs/Li/La, Cs/La/Na,La/S/Sr, K/La/Zr/Ag, Lu/Tl, Pr/Zn, Rb/Sr/La, Na/Sr/Eu/Ca, K/Cs/Sr/La,Na/Sr/Lu, Sr/Eu/Dy, Lu/Nb, La/Dy/Gd, Na/Mg/Tl/P, Na/Pt, Gd/Li/K,Rb/K/Lu, Sr/La/Dy/S, Na/Ce/Co, Na/Ce, Na/Ga/Gd/Al, Ba/Rh/Ta, Ba/Ta,Na/Al/Bi, Cs/Eu/S, Sm/Tm/Yb/Fe, Sm/Tm/Yb, Hf/Zr/Ta, Rb/Gd/Li/K,Gd/Ho/Al/P and Na/Ca/Lu.

In still other embodiments of the foregoing rare earth oxide, the dopantis selected from Ta/Hf, W/Au, Ca/W, Au/Re, Sm/Li, La/K, Zn/Cs, Na/K/Mg,Zr/Cs, Ca/Ce, Na/Li/Cs, Li/Sr, Cs/Zn, La/Dy/K, Dy/K, La/Mg, Na/Nd/In/K,In/Sr, Sr/Cs, Rb/Ga/Tm/Cs, Ga/Cs, K/La/Zr/Ag, Lu/Fe, Sr/Tm, La/Dy,Sm/Li/Sr, Mg/K, Li/Rb/Ga, Li/Cs/Tm, Zr/K, Li/Cs, Li/K/La, Ce/Zr/La,Ca/Al/La, Sr/Zn/La, Sr/Cs/Zn, Sm/Cs, In/K, Ho/Cs/Li/La, Cs/La/Na,La/S/Sr, K/La/Zr/Ag, Lu/Tl, Pr/Zn, Rb/Sr/La, Na/Sr/Eu/Ca, K/Cs/Sr/La,Na/Sr/Lu, Sr/Eu/Dy, Lu/Nb, La/Dy/Gd, Na/Mg/Tl/P, Na/Pt, Gd/Li/K,Li/Sr/Cs, Li/Sr/Zn/K, Li/Ga/Cs, Li/K/Sr/La, Li/Na, Li/Na/Rb/Ga,Li/Na/Sr, Li/Na/Sr/La, Li/Sm/Cs, Ba/Sm/Yb/S, Ba/Tm/K/La, Ba/Tm/Zn/K,Cs/K/La, Cs/La/Tm/Na, Cs/Li/K/La, Sm/Li/Sr/Cs, Sr/Cs/La, Sr/Tm/Li/Cs,Zn/K, Zr/Cs/K/La, Rb/Ca/In/Ni, Sr/Ho/Tm, La/Nd/S, Li/Rb/Ca, Li/K,Tm/Lu/Ta/P, Rb/Ca/Dy/P, Mg/La/Yb/Zn, Rb/Sr/Lu, Na/Sr/Lu/Nb, Na/Eu/Hf,Dy/Rb/Gd, Na/Pt/Bi, Rb/Hf, Ca/Cs, Ca/Mg/Na, Hf/Bi, Sr/Sn, Sr/W, Sr/Nb,Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca, Bi/Sn, Bi/Sb, Ge/Hf, Hf/Sm, Sb/Ag,Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W, Sb/Hf, Sb/Yb, Sb/Sn, Yb/Au, Yb/Ta,Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag, Au/Sr and W/Ge.

In various embodiments of the foregoing rare earth oxides, the catalystscomprise La₂O₃, Nd₂O₃, Yb₂O₃, Eu₂O₃, Y₂O₃, Ce₂O₃, Pr₂O₃ Sm₂O₃,Ln1_(4-x)Ln2_(x)O₆, La_(4-x)Ln1_(x)O₆, La_(4-x)Nd_(x)O₆, wherein Ln1 andLn2 are each independently a lanthanide element, wherein Ln1 and Ln2 arenot the same and x is a number ranging from greater than 0 to less than4, La₃NdO₆, LaNd₃O₆, La_(1.5)Nd_(2.5)O₆, La_(2.5)Nd_(1.5)O₆,La_(3.2)Nd_(0.8)O₆, La_(3.5)Nd_(0.5)O₆, La_(3.8)Nd_(0.2)O₆, Y—La, Zr—La,Pr—La or Ce—La or combinations thereof. In other various embodiments,the rare earth oxide catalyst comprises a C₂ selectivity of greater than50% and a methane conversion of greater than 20% when the rare earthoxide catalyst is employed as a heterogenous catalyst in the oxidativecoupling of methane at a temperature of 750° C. or less.

In other embodiments, the catalysts comprise La₂O₃, Yb₂O₃, Nd₂O₃, Eu₂O₃,Sm₂O₃, Y₂O₃, Ln1_(4-x)Ln2_(x)O₆, La_(4-x)Ln1_(x)O₆, La_(4-x)Nd_(x)O₆,wherein Ln1 and Ln2 are each independently a lanthanide element, whereinLn1 and Ln2 are not the same and x is a number ranging from greater than0 to less than 4, La₃NdO₆, LaNd₃O₆, La_(1.5)Nd_(2.5)O₆,La_(2.5)Nd_(1.5)O₆, La_(3.2)Nd_(0.8)O₆, La_(3.5)Nd_(0.5)O₆,La_(3.8)Nd_(0.2)O₆, Y—La, Zr—La, Pr—La or Ce—La doped with Sr/Ta, forexample in some embodiments the catalysts comprise Sr/Ta/La₂O₃,Sr/Ta/Yb₂O₃, Sr/Ta/Nd₂O₃, Sr/Ta/Eu₂O₃, Sr/Ta/Sm₂O₃,Sr/Ta/Ln1_(4-x)Ln2_(x)O₆, Sr/Ta/La_(4-x)Ln1_(x)O₆,Sr/Ta/La_(4-x)Nd_(x)O₆, Sr/Ta/La₃NdO₆, Sr/Ta/LaNd₃O₆,Sr/Ta/La_(1.5)Nd_(2.5)O₆, Sr/Ta/La_(2.5)Nd_(1.5)O₆,Sr/Ta/La_(3.2)Nd_(0.8)O₆, Sr/Ta/La_(3.5)Nd_(0.5)O₆,Sr/Ta/La_(3.8)Nd_(0.2)O₆, Sr/Ta/Y—La, Sr/Ta/Zr—La, Sr/Ta/Pr—La orSr/Ta/Ce—La or combinations thereof. In other embodiments, the catalystscomprise Ln1_(4-x)Ln2_(x)O₆, La_(4-x)Ln1_(x)O₆, La_(4-x)Nd_(x)O₆,wherein Ln1 and Ln2 are each independently a lanthanide element, whereinLn1 and Ln2 are not the same and x is a number ranging from greater than0 to less than 4, La₃NdO₆, LaNd₃O₆, La_(1.5)Nd_(2.5)O₆,La_(2.5)Nd_(1.5)O₆, La_(3.2)Nd_(0.8)O₆, La_(3.5)Nd_(0.5)O₆,La_(3.8)Nd_(0.2)O₆, Y—La, Zr—La, Pr—La or Ce—La doped with Na, Sr, Ca,Yb, Cs, Sb, or combinations thereof, for example the catalysts maycomprise Na/Ln1_(4-x)Ln2_(x)O₆, Sr/Ln1_(4-x)Ln2_(x)O₆,Ca/Ln1_(4-x)Ln2_(x)O₆, Yb/Ln1_(4-x)Ln2_(x)O₆, Cs/Ln1_(4-x)Ln2_(x)O₆,Sb/Ln1_(4-x)Ln2_(x)O₆, Na/La_(4-x)Ln1_(x)O₆, Na/La₃NdO₆,Sr/La_(4-x)Ln1_(x)O₆, Ca/La_(4-x)Ln1_(x)O₆, Yb/La_(4-x)Ln1_(x)O₆,Cs/La_(4-x)Ln1_(x)O₆, Sb/La_(4-x)Ln1_(x)O₆, Na/La_(4-x)Nd_(x)O₆,Sr/La_(4-x)Nd_(x)O₆, Ca/La_(4-x)Nd_(x)O₆, Yb/La_(4-x)Nd_(x)O₆, CsLa_(4-x)Nd_(x)O₆, Sb/La_(4-x)Nd_(x)O₆, Na/La₃NdO₆, Na/LaNd₃O₆,Na/La_(1.5)Nd_(2.5)O₆, Na/La_(2.5)Nd_(1.5)O₆, Na/La_(3.2)Nd_(0.8)O₆,Na/La_(3.5)Nd_(0.5)O₆, Na/La_(3.8)Nd_(0.2)O₆, Na/Y—La, Na/Zr—La,Na/Pr—La, Na/Ce—La, Sr/La₃NdO₆, Sr/LaNd₃O₆, Sr/La_(1.5)Nd_(2.5)O₆,Sr/La_(2.5)Nd_(1.5)O₆, Sr/La_(3.2)Nd_(0.8)O₆, Sr/La_(3.5)Nd_(0.5)O₆,Sr/La_(3.8)Nd_(0.2)O₆, Sr/Y—La, Sr/Zr—La, Sr/Pr—La, Sr/Ce—La,Ca/La₃NdO₆, Ca/LaNd₃O₆, Ca/La_(1.5)Nd_(2.5)O₆, Ca/La_(2.5)Nd_(1.5)O₆,Ca/La_(3.2)Nd_(0.8)O₆, Ca/La_(3.5)Nd_(0.5)O₆, Ca/La_(3.8)Nd_(0.2)O₆,Ca/Y—La, Ca/Zr—La, Ca/Pr—La, Ca/Ce—La, Yb/La₃NdO₆, Yb/LaNd₃O₆,Yb/La_(1.5)Nd_(2.5)O₆, Yb/La_(2.5)Nd_(1.5)O₆, Yb/La_(3.2)Nd_(0.8)O₆,Yb/La_(3.5)Nd_(0.5)O₆, Yb/La_(3.8)Nd_(0.2)O₆, Yb/Y—La, Yb/Zr—La,Yb/Pr—La, Yb/Ce—La, Cs/La₃NdO₆ LaNd₃O₆, Cs/La_(1.5)Nd_(2.5)O₆,Cs/La_(2.5)Nd_(1.5)O₆, Cs/La_(3.2)Nd_(0.8)O₆, Cs/La_(3.5)Nd_(0.5)O₆,Cs/La_(3.8)Nd_(0.2)O₆, Cs/Y—La, Cs/Zr—La, Cs/Pr—La, Cs/Ce—La,Sb/La₃NdO₆, Sb/LaNd₃O₆, Sb/La_(1.5)Nd_(2.5)O₆, Sb/La_(2.5)Nd_(1.5)O₆,Sb/La_(3.2)Nd_(0.8)O₆, Sb/La_(3.5)Nd_(0.5)O₆, Sb/La_(3.8)Nd_(0.2)O₆,Sb/Y—La, Sb/Zr—La, Sb/Pr—La, Sb/Ce—La or combinations thereof.

In other embodiments, the catalysts comprise a mixed oxide selected froma Y—La mixed oxide doped with Na. (Y ranges from 5 to 20% of La at/at);a Zr—La mixed oxide doped with Na (Zr ranges from 1 to 5% of La at/at);a Pr—La mixed oxide doped with a group 1 element (Pr ranges from 2 to 6%of La at/at); and a Ce—La mixed oxide doped with a group 1 element (Ceranges from 5 to 20% of La at/at). As used herein, the notation “M1-M2”,wherein M1 and M2 are each independently metals refers to a mixed metaloxide comprising the two metals. M1 and M2 may be present in equal ordifferent amounts (at/at).

In still other embodiments, the catalysts comprise a mixed oxide of arare earth element and a Group 13 element, wherein the catalyst furthercomprises one or more Group 2 elements. In certain embodiments of theforegoing, the Group 13 element is B, Al, Ga or In. In otherembodiments, the Group 2 element is Ca or Sr. In still otherembodiments, the rare earth element is La, Y, Nd, Yb, Sm, Pr, Ce or Eu.

Specific examples of the foregoing include, but are not limited toCaLnBO_(x), CaLnAlO_(x), CaLnGaO_(x), CaLnInO_(x), CaLnAlSrO_(x) andCaLnAlSrO_(x), wherein Ln is a lanthanide or yttrium and x is numbersuch that all charges are balanced. For example, in some embodiments thecatalyst comprises CaLaBO₄, CaLaAlO₄, CaLaGaO₄, CaLaInO₄, CaLaAlSrO₅,CaLaAlSrO₅, CaNdBO₄, CaNdAlO₄, CaNdGaO₄, CaNdInO₄, CaNdAlSrO₄,CaNdAlSrO₄, CaYbBO₄, CaYbAlO₄, CaYbGaO₄, CaYbInO₄, CaYbAlSrO₅,CaYbAlSrO₅, CaEuBO₄, CaEuAlO₄, CaEuGaO₄, CaEuInO₄, CaEuAlSrO₅,CaEuAlSrO₅, CaSmBO₄, CaSmAlO₄, CaSmGaO₄, CaSmInO₄, CaSmAlSrO₅,CaSmAlSrO₅, CaYBO₄, CaYAlO₄, CaYGaO₄, CaYInO₄, CaYAlSrO₅, CaYAlSrO₅,CaCeBO₄, CaCeAlO₄, CaCeGaO₄, CaCeInO₄, CaCeAlSrO₅, CaCeAlSrO₅, CaPrBO₄,CaPrAlO₄, CaPrGaO₄, CaPrInO₄, CaPrAlSrO₅ or CaPrAlSrO₅.

Furthermore, the present inventors have discovered that lanthanideoxides doped with alkali metals and/or alkaline earth metals and atleast one other dopant selected from Groups 3-16 have desirablecatalytic properties and are useful in a variety of catalytic reactions,such as OCM. Accordingly, in one embodiment the catalysts comprise alanthanide oxide doped with an alkali metal, an alkaline earth metal orcombinations thereof, and at least one other dopant from groups 3-16. Insome embodiments, the catalyst comprises a lanthanide oxide, an alkalimetal dopant and at least one other dopant selected from Groups 3-16. Inother embodiments, the catalyst comprises a lanthanide oxide, analkaline earth metal dopant and at least one other dopant selected fromGroups 3-16.

In some more specific embodiments of the foregoing, the catalystcomprises a lanthanide oxide, a lithium dopant and at least one otherdopant selected from Groups 3-16. In still other embodiments, thecatalyst comprises a lanthanide oxide, a sodium dopant and at least oneother dopant selected from Groups 3-16. In other embodiments, thecatalyst comprises a lanthanide oxide, a potassium dopant and at leastone other dopant selected from Groups 3-16. In other embodiments, thecatalyst comprises a lanthanide oxide, a rubidium dopant and at leastone other dopant selected from Groups 3-16. In more embodiments, thecatalyst comprises a lanthanide oxide, a caesium dopant and at least oneother dopant selected from Groups 3-16.

In still other embodiments of the foregoing, the catalyst comprises alanthanide oxide, a beryllium dopant and at least one other dopantselected from Groups 3-16. In other embodiments, the catalyst comprisesa lanthanide oxide, a magnesium dopant and at least one other dopantselected from Groups 3-16. In still other embodiments, the catalystcomprises a lanthanide oxide, a calcium dopant and at least one otherdopant selected from Groups 3-16. In more embodiments, the catalystcomprises a lanthanide oxide, a strontium dopant and at least one otherdopant selected from Groups 3-16. In more embodiments, the catalystcomprises a lanthanide oxide, a barium dopant and at least one otherdopant selected from Groups 3-16.

In some embodiments of the foregoing lanthanide oxide catalysts, thecatalysts comprise La₂O₃, Nd₂O₃, Yb₂O₃, Eu₂O₃, Sm₂O₃,Ln1_(4-x)Ln2_(x)O₆, La_(4-x)Ln1_(x)O₆, La_(4-x)Nd_(x)O₆, wherein Ln1 andLn2 are each independently a lanthanide element, wherein Ln1 and Ln2 arenot the same and x is a number ranging from greater than 0 to less than4, La₃NdO₆, LaNd₃O₆, La_(1.5)Nd_(2.5)O₆, La_(2.5)Nd_(1.5)O₆,La_(3.2)Nd_(0.8)O₆, La_(3.5)Nd_(0.5)O₆, La_(3.8)Nd_(0.2)O₆, Y—La, Zr—La,Pr—La or Ce—La or combinations thereof. In other various embodiments,the lanthanide oxide catalyst comprises a C₂ selectivity of greater than50% and a methane conversion of greater than 20% when the lanthanideoxide catalyst is employed as a heterogenous catalyst in the oxidativecoupling of methane at a temperature of 750° C. or less.

In various embodiments, of any of the above catalysts, the catalystcomprises a C₂ selectivity of greater than 50% and a methane conversionof greater than 20% when the catalyst is employed as a heterogenouscatalyst in the oxidative coupling of methane at a temperature of 750°C. or less, 700° C. or less, 650° C. or less or even 600° C. or less.

In more embodiments, of any of the above catalysts, the catalystcomprises a C₂ selectivity of greater than 50%, greater than 55%,greater than 60%, greater than 65%, greater than 70%, or even greaterthan 75%, and a methane conversion of greater than 20% when the catalystis employed as a heterogenous catalyst in the oxidative coupling ofmethane at a temperature of 750° C. or less.

In other embodiments, of any of the above catalysts, the catalystcomprises a C₂ selectivity of greater than 50%, and a methane conversionof greater than 20%, greater than 25%, greater than 30%, greater than35%, greater than 40%, greater than 45%, or even greater than 50% whenthe catalyst is employed as a heterogenous catalyst in the oxidativecoupling of methane at a temperature of 750° C. or less. In someembodiments of the foregoing, the methan conversion and C2 selectivityare calculated based on a single pass basis (i.e., the percent ofmethane converted or C2 selectivity upon a single pass over the catalystor catalytic bed, etc.)

The metal oxides disclosed herein can be in the form of oxides,oxyhydroxides, hydroxides, oxycarbonates or combination thereof afterbeing exposed to moisture, carbon dioxide, undergoing incompletecalcination or combination thereof.

The foregoing doped catalysts comprise 1, 2, 3, 4 or more dopingelements. In this regard, each dopant may be present in the catalysts(for example any of the catalysts described above and/or disclosed inTables 1-4) in up to 75% by weight of the catalyst. For example, in oneembodiment the concentration of a first doping element ranges from 0.01%to 1 w/w, 1%-5% w/w, 5%-10% w/w. 10%-20% ww, 20%-30% w/w, 30%-40% w/w or40%-50% w/w, for example about 1% w/w, about 2% w/w, about 3% w/w, about4% w/w, about 5% w/w, about 6% w/w, about 7% w/w, about 8% w/w, about 9%w/w, about 10% w/w, about 11% w/w, about 12% w/w, about 13% w/w. about14% w/w, about 15% w/w, about 16% w/w, about 17% w/w, about 18% w/w,about 19% w/w or about 20% w/w.

In other embodiments, the concentration of a second doping element (whenpresent) ranges from 0.01% to 1% w/w, 1%-5% w/w, 5%-10% w/w. 10%-20% ww,20%-30% w/w, 30%-40% w/w or 40%-50% w/w, for example about 1% w/w, about2% w/w, about 3% w/w, about 4% w/w, about 5% w/w, about 6% w/w, about 7%w/w, about 8% w/w, about 9% w/w, about 10% w/w, about 11% w/w, about 12%w/w, about 13% w/w. about 14% w/w, about 15% w/w, about 16% w/w, about17% w/w, about 18% w/w, about 19% w/w or about 20% w/w.

In other embodiments, the concentration of a third doping element (whenpresent) ranges from 0.01% to 1% w/w, 1%-5% w/w, 5%-10% w/w. 10%-20% ww,20%-30% w/w, 30%-40% w/w or 40%-50% w/w, for example about 1% w/w, about2% w/w, about 3% w/w, about 4% w/w, about 5% w/w, about 6% w/w, about 7%w/w, about 8% w/w, about 9% w/w, about 10% w/w, about 11% w/w, about 12%w/w, about 13% w/w. about 14% w/w, about 15% w/w, about 16% w/w, about17% w/w, about 18% w/w, about 19% w/w or about 20% w/w.

In other embodiments, the concentration of a fourth doping element (whenpresent) ranges from 0.01% to 1% w/w, 1%-5% w/w, 5%-10% w/w. 10%-20% ww,20%-30% w/w, 30%-40% w/w or 40%-50% w/w, for example about 1% w/w, about2% w/w, about 3% w/w, about 4% w/w, about 5% w/w, about 6% w/w, about 7%w/w, about 8% w/w, about 9% w/w, about 10% w/w, about 11% w/w, about 12%w/w, about 13% w/w. about 14% w/w, about 15% w/w, about 16% w/w, about17% w/w, about 18% w/w, about 19% w/w or about 20% w/w.

In other embodiments, the concentration of the dopant is measured interms of atomic percent (at/at). In some of these embodiments, eachdopant may be present in the catalysts (for example any of the catalystsdescribed above and/or disclosed in Tables 1-4) in up to 75% at/at. Forexample, in one embodiment the concentration of a first doping elementranges from 0.01% to 1% at/at, 1%-5% at/at, 5%-10% at/at. 10%-20% at/at,20%-30% at/at, 30%-40% at/at or 40%-50% at/at, for example about 1%at/at, about 2% at/at, about 3% at/at, about 4% at/at, about 5% at/at,about 6% at/at, about 7% at/at, about 8% at/at, about 9% at/at, about10% at/at, about 11% at/at, about 12% at/at, about 13% at/at. about 14%at/at, about 15% at/at, about 16% at/at, about 17% at/at, about 18%at/at, about 19% at/at or about 20% at/at.

In other embodiments, the concentration of a second doping element (whenpresent) ranges from 0.01% to 1% at/at, 1%-5% at/at, 5%-10% at/at.10%-20% ww, 20%-30% at/at, 30%-40% at/at or 40%-50% at/at, for exampleabout 1% at/at, about 2% at/at, about 3% at/at, about 4% at/at, about 5%at/at, about 6% at/at, about 7% at/at, about 8% at/at, about 9% at/at,about 10% at/at, about 11% at/at, about 12% at/at, about 13% at/at.about 14% at/at, about 15% at/at, about 16% at/at, about 17% at/at,about 18% at/at, about 19% at/at or about 20% at/at.

In other embodiments, the concentration of a third doping element (whenpresent) ranges from 0.01% to 1% at/at, 1%-5% at/at, 5%-10% at/at.10%-20% ww, 20%-30% at/at, 30%-40% at/at or 40%-50% at/at, for exampleabout 1% at/at, about 2% at/at, about 3% at/at, about 4% at/at, about 5%at/at, about 6% at/at, about 7% at/at, about 8% at/at, about 9% at/at,about 10% at/at, about 11% at/at, about 12% at/at, about 13% at/at.about 14% at/at, about 15% at/at, about 16% at/at, about 17% at/at,about 18% at/at, about 19% at/at or about 20% at/at.

In other embodiments, the concentration of a fourth doping element (whenpresent) ranges from 0.01% to 1% at/at, 1%-5% at/at, 5%-10% at/at.10%-20% ww, 20%-30% at/at, 30%-40% at/at or 40%-50% at/at, for exampleabout 1% at/at, about 2% at/at, about 3% at/at, about 4% at/at, about 5%at/at, about 6% at/at, about 7% at/at, about 8% at/at, about 9% at/at,about 10% at/at, about 11% at/at, about 12% at/at, about 13% at/at.about 14% at/at, about 15% at/at, about 16% at/at, about 17% at/at,about 18% at/at, about 19% at/at or about 20% at/at.

Accordingly, any of the doped catalysts described above or in Tables1-4, may comprise any of the foregoing doping concentrations.

Furthermore, different catalytic characteristics of the above dopedcatalysts can be varied or “tuned” based on the method used to preparethem. Such methods are described in more detail herein and other methodsare known in the art. In addition, the above dopants may be incorporatedeither before or after (or combinations thereof) an optional calcinationstep as described herein.

Tables 1-4 below show exemplary doped catalysts in accordance withvarious specific embodiments. Dopants are shown in the vertical columnsand base catalyst in the horizontal rows. The resulting doped catalystsare shown in the intersecting cells.

TABLE 1 CATALYSTS (CAT) DOPED WITH SPECIFIC DOPANTS (DOP) Dop\Cat La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Eu/Na Eu/Na/ Eu/Na/ Eu/Na/ Eu/Na/ Eu/Na/Eu/Na/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sr/Na Sr/Na/ Sr/Na/ Sr/Na/Sr/Na/ Sr/Na/ Sr/Na/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/Zr/Eu/CaNa/Zr/Eu/Ca/ Na/Zr/Eu/Ca/ Na/Zr/Eu/Ca/ Na/Zr/Eu/Ca/ Na/Zr/Eu/Ca/Na/Zr/Eu/Ca/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Mg/Na Mg/Na/ Mg/Na/Mg/Na/ Mg/Na/ Mg/Na/ Mg/Na/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Sr/Sm/Ho/Tm Sr/Sm/Ho/Tm/ Sr/Sm/Ho/Tm/ Sr/Sm/Ho/Tm/ Sr/Sm/Ho/Tm/Sr/Sm/Ho/Tm/ Sr/Sm/Ho/Tm/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sr/WSr/W/ Sr/W/ Sr/W/ Sr/W/ Sr/W/ Sr/W/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Mg/La/K Mg/La/K/ Mg/La/K/ Mg/La/K/ Mg/La/K/ Mg/La/K/ Mg/La/K/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/K/Mg/Tm Na/K/Mg/Tm/ Na/K/Mg/Tm/Na/K/Mg/Tm/ Na/K/Mg/Tm/ Na/K/Mg/Tm/ Na/K/Mg/Tm/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Na/Dy/K Na/Dy/K/ Na/Dy/K/ Na/Dy/K/ Na/Dy/K/ Na/Dy/K/Na/Dy/K/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/La/Dy Na/La/Dy/Na/La/Dy/ Na/La/Dy/ Na/La/Dy/ Na/La/Dy/ Na/La/Dy/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/La/Eu Na/La/Eu/ Na/La/Eu/ Na/La/Eu/ Na/La/Eu/Na/La/Eu/ Na/La/Eu/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/La/Eu/InNa/La/Eu/In/ Na/La/Eu/In/ Na/La/Eu/In/ Na/La/Eu/In/ Na/La/Eu/In/Na/La/Eu/In/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/La/K Na/La/K/Na/La/K/ Na/La/K/ Na/La/K/ Na/La/K/ Na/La/K/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Na/La/Li/Cs Na/La/Li/Cs/ Na/La/Li/Cs/ Na/La/Li/Cs/Na/La/Li/Cs/ Na/La/Li/Cs/ Na/La/Li/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ K/La/ K/La/ K/La/ K/La/ K/La/ K/La/ K/La La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ K/La/S K/La/S/ K/La/S/ K/La/S/ K/La/S/ K/La/S/ K/La/S/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ K/Na K/Na/ K/Na/ K/Na/ K/Na/ K/Na/K/Na/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Cs Li/Cs/ Li/Cs/ Li/Cs/Li/Cs/ Li/Cs/ Li/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Cs/LaLi/Cs/La/ Li/Cs/La/ Li/Cs/La/ Li/Cs/La/ Li/Cs/La/ Li/Cs/La/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Cs/La/Tm Li/Cs/La/Tm/ Li/Cs/La/Tm/Li/Cs/La/Tm/ Li/Cs/La/Tm/ Li/Cs/La/Tm/ Li/Cs/La/Tm/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Cs/Sr/Tm Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Li/Sr/Cs Li/Sr/Cs/ Li/Sr/Cs/ Li/Sr/Cs/ Li/Sr/Cs/ Li/Sr/Cs/Li/Sr/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Sr/Zn/K Li/Sr/Zn/K/Li/Sr/Zn/K/ Li/Sr/Zn/K/ Li/Sr/Zn/K/ Li/Sr/Zn/K/ Li/Sr/Zn/K/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Ga/Cs Li/Ga/Cs/ Li/Ga/Cs/ Li/Ga/Cs/Li/Ga/Cs/ Li/Ga/Cs/ Li/Ga/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Li/K/Sr/La Li/K/Sr/La/ Li/K/Sr/La/ Li/K/Sr/La/ Li/K/Sr/La/ Li/K/Sr/La/Li/K/Sr/La/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Na Li/Na/ Li/Na/Li/Na/ Li/Na/ Li/Na/ Li/Na/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Li/Na/Rb/Ga Li/Na/Rb/Ga/ Li/Na/Rb/Ga/ Li/Na/Rb/Ga/ Li/Na/Rb/Ga/Li/Na/Rb/Ga/ Li/Na/Rb/Ga/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Na/SrLi/Na/Sr/ Li/Na/Sr/ Li/Na/Sr/ Li/Na/Sr/ Li/Na/Sr/ Li/Na/Sr/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Na/Sr/La Li/Na/Sr/La/ Li/Na/Sr/La/Li/Na/Sr/La/ Li/Na/Sr/La/ Li/Na/Sr/La/ Li/Na/Sr/La/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Sm/Cs Li/Sm/Cs/ Li/Sm/Cs/ Li/Sm/Cs/ Li/Sm/Cs/Li/Sm/Cs/ Li/Sm/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ba/Sm/Yb/SBa/Sm/Yb/S/ Ba/Sm/Yb/S/ Ba/Sm/Yb/S/ Ba/Sm/Yb/S/ Ba/Sm/Yb/S/ Ba/Sm/Yb/S/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ba/Tm/K/La Ba/Tm/K/La/ Ba/Tm/K/La/Ba/Tm/K/La/ Ba/Tm/K/La/ Ba/Tm/K/La/ Ba/Tm/K/La/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Ba/Tm/Zn/K Ba/Tm/Zn/K/ Ba/Tm/Zn/K/ Ba/Tm/Zn/K/ Ba/Tm/Zn/K/Ba/Tm/Zn/K/ Ba/Tm/Zn/K/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Cs/K/LaCs/K/La/ Cs/K/La/ Cs/K/La/ Cs/K/La/ Cs/K/La/ Cs/K/La/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Cs/La/Tm/Na Cs/La/Tm/Na/ Cs/La/Tm/Na/ Cs/La/Tm/Na/Cs/La/Tm/Na/ Cs/La/Tm/Na/ Cs/La/Tm/Na/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Cs/Li/K/La Cs/Li/K/La/ Cs/Li/K/La/ Cs/Li/K/La/ Cs/Li/K/La/Cs/Li/K/La/ Cs/Li/K/La/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Sm/Li/Sr/Cs Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sr/Cs/LaSr/Cs/La/ Sr/Cs/La/ Sr/Cs/La/ Sr/Cs/La/ Sr/Cs/La/ Sr/Cs/La/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sr/Tm/Li/Cs Sr/Tm/Li/Cs/ Sr/Tm/Li/Cs/Sr/Tm/Li/Cs/ Sr/Tm/Li/Cs/ Sr/Tm/Li/Cs/ Sr/Tm/Li/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Zn/K Zn/K/ Zn/K/ Zn/K/ Zn/K/ Zn/K/ Zn/K/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Zr/Cs/K/La Zr/Cs/K/La/ Zr/Cs/K/La/ Zr/Cs/K/La/Zr/Cs/K/La/ Zr/Cs/K/La/ Zr/Cs/K/La/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Rb/Ca/In/Ni Rb/Ca/In/Ni/ Rb/Ca/In/Ni/ Rb/Ca/In/Ni/ Rb/Ca/In/Ni/Rb/Ca/In/Ni/ Rb/Ca/In/Ni/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sr/Ho/TmSr/Ho/Tm/ Sr/Ho/Tm/ Sr/Ho/Tm/ Sr/Ho/Tm/ Sr/Ho/Tm/ Sr/Ho/Tm/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ La/Nd/S La/Nd/S/ La/Nd/S/ La/Nd/S/ La/Nd/S/La/Nd/S/ La/Nd/S/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Rb/CaLi/Rb/Ca/ Li/Rb/Ca/ Li/Rb/Ca/ Li/Rb/Ca/ Li/Rb/Ca/ Li/Rb/Ca/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/K Li/K/ Li/K/ Li/K/ Li/K/ Li/K/ Li/K/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Tm/Lu/Ta/P Tm/Lu/Ta/P/ Tm/Lu/Ta/P/Tm/Lu/Ta/P/ Tm/Lu/Ta/P/ Tm/Lu/Ta/P/ Tm/Lu/Ta/P/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Rb/Ca/Dy/P Rb/Ca/Dy/P/ Rb/Ca/Dy/P/ Rb/Ca/Dy/P/ Rb/Ca/Dy/P/Rb/Ca/Dy/P/ Rb/Ca/Dy/P/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Mg/La/Yb/Zn Mg/La/Yb/Zn/ Mg/La/Yb/Zn/ Mg/La/Yb/Zn/ Mg/La/Yb/Zn/Mg/La/Yb/Zn/ Mg/La/Yb/Zn/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Rb/Sr/LuRb/Sr/Lu/ Rb/Sr/Lu/ Rb/Sr/Lu/ Rb/Sr/Lu/ Rb/Sr/Lu/ Rb/Sr/Lu/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/Sr/Lu/Nb Na/Sr/Lu/Nb/ Na/Sr/Lu/Nb/Na/Sr/Lu/Nb/ Na/Sr/Lu/Nb/ Na/Sr/Lu/Nb/ Na/Sr/Lu/Nb/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/Eu/Hf Na/Eu/Hf/ Na/Eu/Hf/ Na/Eu/Hf/ Na/Eu/Hf/Na/Eu/Hf/ Na/Eu/Hf/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Dy/Rb/GdDy/Rb/Gd/ Dy/Rb/Gd/ Dy/Rb/Gd/ Dy/Rb/Gd/ Dy/Rb/Gd/ Dy/Rb/Gd/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/Pt/Bi Na/Pt/Bi/ Na/Pt/Bi/ Na/Pt/Bi/Na/Pt/Bi/ Na/Pt/Bi/ Na/Pt/Bi/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Rb/Hf Rb/Hf/ Rb/Hf/ Rb/Hf/ Rb/Hf/ Rb/Hf/ Rb/Hf/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Ca/Cs Ca/Cs/ Ca/Cs/ Ca/Cs/ Ca/Cs/ Ca/Cs/ Ca/Cs/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ca/Mg/Na Ca/Mg/Na/ Ca/Mg/Na/ Ca/Mg/Na/Ca/Mg/Na/ Ca/Mg/Na/ Ca/Mg/Na/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Hf/Bi Hf/Bi/ Hf/Bi/ Hf/Bi/ Hf/Bi/ Hf/Bi/ Hf/Bi/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Sr/Sn Sr/Sn/ Sr/Sn/ Sr/Sn/ Sr/Sn/ Sr/Sn/ Sr/Sn/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sr/W Sr/W/ Sr/W/ Sr/W/ Sr/W/ Sr/W/ Sr/W/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sr/Nb Sr/Nb/ Sr/Nb/ Sr/Nb/ Sr/Nb/Sr/Nb/ Sr/Nb/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Zr/W Zr/W/ Zr/W/Zr/W/ Zr/W/ Zr/W/ Zr/W/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Y/W Y/W/Y/W/ Y/W/ Y/W/ Y/W/ Y/W/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/WNa/W/ Na/W/ Na/W/ Na/W/ Na/W/ Na/W/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Bi/W Bi/W/ Bi/W/ Bi/W/ Bi/W/ Bi/W/ Bi/W/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Bi/Cs Bi/Cs/ Bi/Cs/ Bi/Cs/ Bi/Cs/ Bi/Cs/ Bi/Cs/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Bi/Ca Bi/Ca/ Bi/Ca/ Bi/Ca/ Bi/Ca/ Bi/Ca/Bi/Ca/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Bi/Sn Bi/Sn/ Bi/Sn/ Bi/Sn/Bi/Sn/ Bi/Sn/ Bi/Sn/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Bi/Sb Bi/Sb/Bi/Sb/ Bi/Sb/ Bi/Sb/ Bi/Sb/ Bi/Sb/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Ge/Hf Ge/Hf/ Ge/Hf/ Ge/Hf/ Ge/Hf/ Ge/Hf/ Ge/Hf/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Hf/Sm Hf/Sm/ Hf/Sm/ Hf/Sm/ Hf/Sm/ Hf/Sm/ Hf/Sm/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sb/Ag Sb/Ag/ Sb/Ag/ Sb/Ag/ Sb/Ag/ Sb/Ag/Sb/Ag/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sb/Bi Sb/Bi/ Sb/Bi/ Sb/Bi/Sb/Bi/ Sb/Bi/ Sb/Bi/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sb/Au Sb/Au/Sb/Au/ Sb/Au/ Sb/Au/ Sb/Au/ Sb/Au/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Sb/Sm Sb/Sm/ Sb/Sm/ Sb/Sm/ Sb/Sm/ Sb/Sm/ Sb/Sm/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Sb/Sr Sb/Sr/ Sb/Sr/ Sb/Sr/ Sb/Sr/ Sb/Sr/ Sb/Sr/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sb/W Sb/W/ Sb/W/ Sb/W/ Sb/W/ Sb/W/ Sb/W/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sb/Hf Sb/Hf/ Sb/Hf/ Sb/Hf/ Sb/Hf/Sb/Hf/ Sb/Hf/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sb/Yb Sb/Yb/ Sb/Yb/Sb/Yb/ Sb/Yb/ Sb/Yb/ Sb/Yb/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sb/SnSb/Sn/ Sb/Sn/ Sb/Sn/ Sb/Sn/ Sb/Sn/ Sb/Sn/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Yb/Au Yb/Au/ Yb/Au/ Yb/Au/ Yb/Au/ Yb/Au/ Yb/Au/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Yb/Ta Yb/Ta/ Yb/Ta/ Yb/Ta/ Yb/Ta/ Yb/Ta/Yb/Ta/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Yb/W Yb/W/ Yb/W/ Yb/W/Yb/W/ Yb/W/ Yb/W/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Yb/Sr Yb/Sr/Yb/Sr/ Yb/Sr/ Yb/Sr/ Yb/Sr/ Yb/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Yb/Pb Yb/Pb/ Yb/Pb/ Yb/Pb/ Yb/Pb/ Yb/Pb/ Yb/Pb/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Yb/Ag Yb/Ag/ Yb/Ag/ Yb/Ag/ Yb/Ag/ Yb/Ag/ Yb/Ag/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Au/Sr Au/Sr/ Au/Sr/ Au/Sr/ Au/Sr/ Au/Sr/Au/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ W/Ge W/Ge/ W/Ge/ W/Ge/W/Ge/ W/Ge/ W/Ge/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ta/Sr Ta/Sr/Ta/Sr/ Ta/Sr/ Ta/Sr/ Ta/Sr/ Ta/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Ta/Hf Ta/Hf/ Ta/Hf/ Ta/Hf/ Ta/Hf/ Ta/Hf/ Ta/Hf/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ W/Au W/Au/ W/Au/ W/Au/ W/Au/ W/Au/ W/Au/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Ca/W Ca/W/ Ca/W/ Ca/W/ Ca/W/ Ca/W/ Ca/W/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Au/Re Au/Re/ Au/Re/ Au/Re/ Au/Re/ Au/Re/Au/Re/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sm/Li Sm/Li/ Sm/Li/ Sm/Li/Sm/Li/ Sm/Li/ Sm/Li/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ La/K La/K/La/K/ La/K/ La/K/ La/K/ La/K/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Zn/Cs Zn/Cs/ Zn/Cs/ Zn/Cs/ Zn/Cs/ Zn/Cs/ Zn/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Na/K/Mg Na/K/Mg/ Na/K/Mg/ Na/K/Mg/ Na/K/Mg/ Na/K/Mg/Na/K/Mg/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Zr/Cs Zr/Cs/ Zr/Cs/Zr/Cs/ Zr/Cs/ Zr/Cs/ Zr/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ca/CeCa/Ce/ Ca/Ce/ Ca/Ce/ Ca/Ce/ Ca/Ce/ Ca/Ce/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Na/Li/Cs Na/Li/Cs/ Na/Li/Cs/ Na/Li/Cs/ Na/Li/Cs/ Na/Li/Cs/Na/Li/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Sr Li/Sr/ Li/Sr/Li/Sr/ Li/Sr/ Li/Sr/ Li/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆La/Dy/K La/Dy/K/ La/Dy/K/ La/Dy/K/ La/Dy/K/ La/Dy/K/ La/Dy/K/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Dy/K Dy/K/ Dy/K/ Dy/K/ Dy/K/ Dy/K/ Dy/K/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ La/Mg La/Mg/ La/Mg/ La/Mg/ La/Mg/La/Mg/ La/Mg/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/Nd/In/KNa/Nd/In/K/ Na/Nd/In/K/ Na/Nd/In/K/ Na/Nd/In/K/ Na/Nd/In/K/ Na/Nd/In/K/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ In/Sr In/Sr/ In/Sr/ In/Sr/ In/Sr/In/Sr/ In/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sr/Cs Sr/Cs/ Sr/Cs/Sr/Cs/ Sr/Cs/ Sr/Cs/ Sr/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Rb/Ga/Tm/Cs Rb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/Rb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ga/CsGa/Cs/ Ga/Cs/ Ga/Cs/ Ga/Cs/ Ga/Cs/ Ga/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ K/La/Zr/Ag K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/K/La/Zr/Ag/ K/La/Zr/Ag/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Lu/FeLu/Fe/ Lu/Fe/ Lu/Fe/ Lu/Fe/ Lu/Fe/ Lu/Fe/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Sr/Tm Sr/Tm/ Sr/Tm/ Sr/Tm/ Sr/Tm/ Sr/Tm/ Sr/Tm/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ La/Dy La/Dy/ La/Dy/ La/Dy/ La/Dy/ La/Dy/La/Dy/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sm/Li/Sr Sm/Li/Sr/Sm/Li/Sr/ Sm/Li/Sr/ Sm/Li/Sr/ Sm/Li/Sr/ Sm/Li/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Mg/K Mg/K/ Mg/K/ Mg/K/ Mg/K/ Mg/K/ Mg/K/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Rb/Ga Li/Rb/Ga/ Li/Rb/Ga/ Li/Rb/Ga/Li/Rb/Ga/ Li/Rb/Ga/ Li/Rb/Ga/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Li/Cs/Tm Li/Cs/Tm/ Li/Cs/Tm/ Li/Cs/Tm/ Li/Cs/Tm/ Li/Cs/Tm/ Li/Cs/Tm/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Zr/K Zr/K/ Zr/K/ Zr/K/ Zr/K/ Zr/K/Zr/K/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/Cs Li/Cs/ Li/Cs/ Li/Cs/Li/Cs/ Li/Cs/ Li/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Li/K/LaLi/K/La/ Li/K/La/ Li/K/La/ Li/K/La/ Li/K/La/ Li/K/La/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Ce/Zr/La Ce/Zr/La/ Ce/Zr/La/ Ce/Zr/La/ Ce/Zr/La/Ce/Zr/La/ Ce/Zr/La/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ca/Al/LaCa/Al/La/ Ca/Al/La/ Ca/Al/La/ Ca/Al/La/ Ca/Al/La/ Ca/Al/La/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sr/Zn/La Sr/Zn/La/ Sr/Zn/La/ Sr/Zn/La/Sr/Zn/La/ Sr/Zn/La/ Sr/Zn/La/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Sr/Cs/Zn Sr/Cs/Zn/ Sr/Cs/Zn/ Sr/Cs/Zn/ Sr/Cs/Zn/ Sr/Cs/Zn/ Sr/Cs/Zn/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sm/Cs Sm/Cs/ Sm/Cs/ Sm/Cs/ Sm/Cs/Sm/Cs/ Sm/Cs/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ In/K In/K/ In/K/In/K/ In/K/ In/K/ In/K/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Ho/Cs/Li/La Ho/Cs/Li/La/ Ho/Cs/Li/La/ Ho/Cs/Li/La/ Ho/Cs/Li/La/Ho/Cs/Li/La/ Ho/Cs/Li/La/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Cs/La/NaCs/La/Na/ Cs/La/Na/ Cs/La/Na/ Cs/La/Na/ Cs/La/Na/ Cs/La/Na/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ La/S/Sr La/S/Sr/ La/S/Sr/ La/S/Sr/ La/S/Sr/La/S/Sr/ La/S/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ K/La/Zr/AgK/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Lu/Tl Lu/Tl/ Lu/Tl/ Lu/Tl/ Lu/Tl/Lu/Tl/ Lu/Tl/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Pr/Zn Pr/Zn/ Pr/Zn/Pr/Zn/ Pr/Zn/ Pr/Zn/ Pr/Zn/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Rb/Sr/La Rb/Sr/La/ Rb/Sr/La/ Rb/Sr/La/ Rb/Sr/La/ Rb/Sr/La/ Rb/Sr/La/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/Sr/Eu/Ca Na/Sr/Eu/Ca/Na/Sr/Eu/Ca/ Na/Sr/Eu/Ca/ Na/Sr/Eu/Ca/ Na/Sr/Eu/Ca/ Na/Sr/Eu/Ca/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ K/Cs/Sr/La K/Cs/Sr/La/ K/Cs/Sr/La/K/Cs/Sr/La/ K/Cs/Sr/La/ K/Cs/Sr/La/ K/Cs/Sr/La/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Na/Sr/Lu Na/Sr/Lu/ Na/Sr/Lu/ Na/Sr/Lu/ Na/Sr/Lu/ Na/Sr/Lu/Na/Sr/Lu/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sr/Eu/Dy Sr/Eu/Dy/Sr/Eu/Dy/ Sr/Eu/Dy/ Sr/Eu/Dy/ Sr/Eu/Dy/ Sr/Eu/Dy/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Lu/Nb Lu/Nb/ Lu/Nb/ Lu/Nb/ Lu/Nb/ Lu/Nb/ Lu/Nb/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ La/Dy/Gd La/Dy/Gd/ La/Dy/Gd/La/Dy/Gd/ La/Dy/Gd/ La/Dy/Gd/ La/Dy/Gd/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Na/Mg/Tl/P Na/Mg/Tl/P/ Na/Mg/Tl/P/ Na/Mg/Tl/P/ Na/Mg/Tl/P/Na/Mg/Tl/P/ Na/Mg/Tl/P/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/PtNa/Pt/ Na/Pt/ Na/Pt/ Na/Pt/ Na/Pt/ Na/Pt/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Gd/Li/K Gd/Li/K/ Gd/Li/K/ Gd/Li/K/ Gd/Li/K/ Gd/Li/K/ Gd/Li/K/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Rb/K/Lu Rb/K/Lu/ Rb/K/Lu/ Rb/K/Lu/Rb/K/Lu/ Rb/K/Lu/ Rb/K/Lu/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Sr/La/Dy/S Sr/La/Dy/S/ Sr/La/Dy/S/ Sr/La/Dy/S/ Sr/La/Dy/S/ Sr/La/Dy/S/Sr/La/Dy/S/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/Ce/Co Na/Ce/Co/Na/Ce/Co/ Na/Ce/Co/ Na/Ce/Co/ Na/Ce/Co/ Na/Ce/Co/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/Ce Na/Ce/ Na/Ce/ Na/Ce/ Na/Ce/ Na/Ce/ Na/Ce/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/Ga/Gd/Al Na/Ga/Gd/Al/Na/Ga/Gd/Al/ Na/Ga/Gd/Al/ Na/Ga/Gd/Al/ Na/Ga/Gd/Al/ Na/Ga/Gd/Al/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ba/Rh/Ta Ba/Rh/Ta/ Ba/Rh/Ta/ Ba/Rh/Ta/Ba/Rh/Ta/ Ba/Rh/Ta/ Ba/Rh/Ta/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Ba/Ta Ba/Ta/ Ba/Ta/ Ba/Ta/ Ba/Ta/ Ba/Ta/ Ba/Ta/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Na/Al/Bi Na/Al/Bi/ Na/Al/Bi/ Na/Al/Bi/ Na/Al/Bi/ Na/Al/Bi/Na/Al/Bi/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Cs/Eu/S Cs/Eu/S/Cs/Eu/S/ Cs/Eu/S/ Cs/Eu/S/ Cs/Eu/S/ Cs/Eu/S/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Sm/Tm/Yb/Fe Sm/Tm/Yb/Fe/ Sm/Tm/Yb/Fe/ Sm/Tm/Yb/Fe/Sm/Tm/Yb/Fe/ Sm/Tm/Yb/Fe/ Sm/Tm/Yb/Fe/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Sm/Tm/Yb Sm/Tm/Yb/ Sm/Tm/Yb/ Sm/Tm/Yb/ Sm/Tm/Yb/ Sm/Tm/Yb/Sm/Tm/Yb/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Hf/Zr/Ta Hf/Zr/Ta/Hf/Zr/Ta/ Hf/Zr/Ta/ Hf/Zr/Ta/ Hf/Zr/Ta/ Hf/Zr/Ta/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Rb/Gd/Li/K Rb/Gd/Li/K/ Rb/Gd/Li/K/ Rb/Gd/Li/K/Rb/Gd/Li/K/ Rb/Gd/Li/K/ Rb/Gd/Li/K/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Gd/Ho/Al/P Gd/Ho/Al/P/ Gd/Ho/Al/P/ Gd/Ho/Al/P/ Gd/Ho/Al/P/Gd/Ho/Al/P/ Gd/Ho/Al/P/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na/Ca/LuNa/Ca/Lu/ Na/Ca/Lu/ Na/Ca/Lu/ Na/Ca/Lu/ Na/Ca/Lu/ Na/Ca/Lu/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Cu/Sn Cu/Sn/ Cu/Sn/ Cu/Sn/ Cu/Sn/ Cu/Sn/Cu/Sn/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ag/Au Ag/Au/ Ag/Au/ Ag/Au/Ag/Au/ Ag/Au/ Ag/Au/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Al/Bi Al/Bi/Al/Bi/ Al/Bi/ Al/Bi/ Al/Bi/ Al/Bi/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Al/Mo Al/Mo/ Al/Mo/ Al/Mo/ Al/Mo/ Al/Mo/ Al/Mo/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Al/Nb Al/Nb/ Al/Nb/ Al/Nb/ Al/Nb/ Al/Nb/ Al/Nb/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Au/Pt Au/Pt/ Au/Pt/ Au/Pt/ Au/Pt/ Au/Pt/Au/Pt/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ga/Bi Ga/Bi/ Ga/Bi/ Ga/Bi/Ga/Bi/ Ga/Bi/ Ga/Bi/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Mg/W Mg/W/Mg/W/ Mg/W/ Mg/W/ Mg/W/ Mg/W/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Pb/Au Pb/Au/ Pb/Au/ Pb/Au/ Pb/Au/ Pb/Au/ Pb/Au/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Sn/Mg Sn/Mg/ Sn/Mg/ Sn/Mg/ Sn/Mg/ Sn/Mg/ Sn/Mg/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Zn/Bi Zn/Bi/ Zn/Bi/ Zn/Bi/ Zn/Bi/ Zn/Bi/Zn/Bi/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sr/Ta Sr/Ta/ Sr/Ta/ Sr/Ta/Sr/Ta/ Sr/Ta/ Sr/Ta/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Na Na/ Na/Na/ Na/ Na/ Na/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sr Sr/ Sr/ Sr/ Sr/Sr/ Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ca Ca/ Ca/ Ca/ Ca/ Ca/ Ca/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Yb Yb/ Yb/ Yb/ Yb/ Yb/ Yb/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Cs Cs/ Cs/ Cs/ Cs/ Cs/ Cs/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sb Sb/ Sb/ Sb/ Sb/ Sb/ Sb/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Gd/Ho Gd/Ho/ Gd/Ho/ Gd/Ho/ Gd/Ho/ Gd/Ho/ Gd/Ho/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Zr/Bi Zr/Bi/ Zr/Bi/ Zr/Bi/ Zr/Bi/Zr/Bi/ Zr/Bi/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ho/Sr Ho/Sr/ Ho/Sr/Ho/Sr/ Ho/Sr/ Ho/Sr/ Ho/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Gd/Ho/Sr Gd/Ho/Sr/ Gd/Ho/Sr/ Gd/Ho/Sr/ Gd/Ho/Sr/ Gd/Ho/Sr/ Gd/Ho/Sr/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ca/Sr Ca/Sr/ Ca/Sr/ Ca/Sr/ Ca/Sr/Ca/Sr/ Ca/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ca/Sr/W Ca/Sr/W/Ca/Sr/W/ Ca/Sr/W/ Ca/Sr/W/ Ca/Sr/W/ Ca/Sr/W/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Na/Zr/Eu/Tm Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Sr/Ho/ Sr/Ho/Tm/Na/ Sr/Ho/Tm/Na/ Sr/Ho/Tm/Na/ Sr/Ho/Tm/Na/Sr/Ho/Tm/Na/ Sr/Ho/Tm/Na/ Tm/Na La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Sr/Pb Sr/Pb/ Sr/Pb/ Sr/Pb/ Sr/Pb/ Sr/Pb/ Sr/Pb/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Sr/W/Li Sr/W/Li/ Sr/W/Li/ Sr/W/Li/ Sr/W/Li/ Sr/W/Li/Sr/W/Li/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Ca/Sr/W Ca/Sr/W/ Ca/Sr/W/Ca/Sr/W/ Ca/Sr/W/ Ca/Sr/W/ Ca/Sr/W/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃La₃NdO₆ Sr/Hf Sr/Hf/ Sr/Hf/ Sr/Hf/ Sr/Hf/ Sr/Hf/ Sr/Hf/ La₂O₃ Nd₂O₃Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Au/Re Au/Re/ Au/Re/ Au/Re/ Au/Re/ Au/Re/Au/Re/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Sr/W Sr/W/ Sr/W/ Sr/W/Sr/W/ Sr/W/ Sr/W/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ La/Nd La/Nd/La/Nd/ La/Nd/ La/Nd/ La/Nd/ La/Nd/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆La/Sm La/Sm/ La/Sm/ La/Sm/ La/Sm/ La/Sm/ La/Sm/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ La/Ce La/Ce/ La/Ce/ La/Ce/ La/Ce/ La/Ce/ La/Ce/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ La/Sr La/Sr/ La/Sr/ La/Sr/ La/Sr/ La/Sr/La/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ La/Nd/Sr La/Nd/Sr/La/Nd/Sr/ La/Nd/Sr/ La/Nd/Sr/ La/Nd/Sr/ La/Nd/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ La/Bi/Sr La/Bi/Sr/ La/Bi/Sr/ La/Bi/Sr/ La/Bi/Sr/La/Bi/Sr/ La/Bi/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ La/Ce/Nd/SrLa/Ce/Nd/Sr/ La/Ce/Nd/Sr/ La/Ce/Nd/Sr/ La/Ce/Nd/Sr/ La/Ce/Nd/Sr/La/Ce/Nd/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ La/Bi/Ce/Nd/La/Bi/Ce/Nd/Sr/ La/Bi/Ce/Nd/Sr/ La/Bi/Ce/Nd/Sr/ La/Bi/Ce/Nd/Sr/La/Bi/Ce/Nd/Sr/ La/Bi/Ce/Nd/Sr/ Sr La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Eu/Gd Eu/Gd/ Eu/Gd/ Eu/Gd/ Eu/Gd/ Eu/Gd/ Eu/Gd/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Ca/Na Ca/Na/ Ca/Na/ Ca/Na/ Ca/Na/ Ca/Na/ Ca/Na/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Eu/Sm Eu/Sm/ Eu/Sm/ Eu/Sm/ Eu/Sm/ Eu/Sm/Eu/Sm/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Eu/Sr Eu/Sr/ Eu/Sr/ Eu/Sr/Eu/Sr/ Eu/Sr/ Eu/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Mg/Sr Mg/Sr/Mg/Sr/ Mg/Sr/ Mg/Sr/ Mg/Sr/ Mg/Sr/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Ce/Mg Ce/Mg/ Ce/Mg/ Ce/Mg/ Ce/Mg/ Ce/Mg/ Ce/Mg/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Gd/Sm Gd/Sm/ Gd/Sm/ Gd/Sm/ Gd/Sm/ Gd/Sm/ Gd/Sm/ La₂O₃Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Au/Pb Au/Pb/ Au/Pb/ Au/Pb/ Au/Pb/ Au/Pb/Au/Pb/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Bi/Hf Bi/Hf/ Bi/Hf/ Bi/Hf/Bi/Hf/ Bi/Hf/ Bi/Hf/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Rb/S Rb/S/Rb/S/ Rb/S/ Rb/S/ Rb/S/ Rb/S/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆Sr/Nd Sr/Nd/ Sr/Nd/ Sr/Nd/ Sr/Nd/ Sr/Nd/ Sr/Nd/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃Sm₂O₃ La₃NdO₆ Eu/Y Eu/Y/ Eu/Y/ Eu/Y/ Eu/Y/ Eu/Y/ Eu/Y/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Mg/Nd Mg/Nd/ Mg/Nd/ Mg/Nd/ Mg/Nd/ Mg/Nd/ Mg/Nd/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ La/Mg La/Mg/ La/Mg/ La/Mg/ La/Mg/La/Mg/ La/Mg/ La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ La₃NdO₆ Mg/Nd/Fe Mg/Nd/Fe/Mg/Nd/Fe/ Mg/Nd/Fe/ Mg/Nd/Fe/ Mg/Nd/Fe/ Mg/Nd/Fe/ La₂O₃ Nd₂O₃ Yb₂O₃Eu₂O₃ Sm₂O₃ La₃NdO₆ Rb/Sr Rb/Sr/ Rb/Sr/ Rb/Sr/ Rb/Sr/ Rb/Sr/ Rb/Sr/La₂O₃ Nd₂O₃ Yb₂O₃ Eu₂O₃ Sm₂O₃ Rb/Sr/

TABLE 2 CATALYSTS (CAT) DOPED WITH SPECIFIC DOPANTS (DOP) Dop\CatLa_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Eu/Na Eu/Na/ Eu/Na/ Eu/Na/ Eu/Na/Eu/Na/ Eu/Na/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/Na Sr/Na/Sr/Na/ Sr/Na/ Sr/Na/ Sr/Na/ Sr/Na/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Na/Zr/Eu/Ca Na/Zr/Eu/Ca/ Na/Zr/Eu/Ca/ Na/Zr/Eu/Ca/Na/Zr/Eu/Ca/ Na/Zr/Eu/Ca/ Na/Zr/Eu/Ca/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Mg/Na Mg/Na/ Mg/Na/ Mg/Na/ Mg/Na/ Mg/Na/ Mg/Na/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/Sm/Ho/Tm Sr/Sm/Ho/Tm/Sr/Sm/Ho/Tm/ Sr/Sm/Ho/Tm/ Sr/Sm/Ho/Tm/ Sr/Sm/Ho/Tm/ Sr/Sm/Ho/Tm/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/W Sr/W/ Sr/W/ Sr/W/ Sr/W/ Sr/W/Sr/W/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Mg/La/K Mg/La/K/ Mg/La/K/ Mg/La/K/Mg/La/K/ Mg/La/K/ Mg/La/K/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/K/Mg/TmNa/K/Mg/Tm/ Na/K/Mg/Tm/ Na/K/Mg/Tm/ Na/K/Mg/Tm/ Na/K/Mg/Tm/ Na/K/Mg/Tm/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/Dy/K Na/Dy/K/ Na/Dy/K/ Na/Dy/K/Na/Dy/K/ Na/Dy/K/ Na/Dy/K/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/La/DyNa/La/Dy/ Na/La/Dy/ Na/La/Dy/ Na/La/Dy/ Na/La/Dy/ Na/La/Dy/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/La/Eu Na/La/Eu/ Na/La/Eu/Na/La/Eu/ Na/La/Eu/ Na/La/Eu/ Na/La/Eu/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Na/La/Eu/In Na/La/Eu/In/ Na/La/Eu/In/ Na/La/Eu/In/Na/La/Eu/In/ Na/La/Eu/In/ Na/La/Eu/In/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Na/La/K Na/La/K/ Na/La/K/ Na/La/K/ Na/La/K/ Na/La/K/Na/La/K/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/La/Li/Cs Na/La/Li/Cs/Na/La/Li/Cs/ Na/La/Li/Cs/ Na/La/Li/Cs/ Na/La/Li/Cs/ Na/La/Li/Cs/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ K/La K/La/ K/La/ K/La/ K/La/ K/La/K/La/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ K/La/S K/La/S/ K/La/S/ K/La/S/K/La/S/ K/La/S/ K/La/S/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ K/Na K/Na/K/Na/ K/Na/ K/Na/ K/Na/ K/Na/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Li/Cs Li/Cs/ Li/Cs/ Li/Cs/ Li/Cs/ Li/Cs/ Li/Cs/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Li/Cs/La Li/Cs/La/ Li/Cs/La/Li/Cs/La/ Li/Cs/La/ Li/Cs/La/ Li/Cs/La/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Li/Cs/La/Tm Li/Cs/La/Tm/ Li/Cs/La/Tm/ Li/Cs/La/Tm/Li/Cs/La/Tm/ Li/Cs/La/Tm/ Li/Cs/La/Tm/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Li/Cs/Sr/Tm Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Li/Sr/Cs Li/Sr/Cs/ Li/Sr/Cs/ Li/Sr/Cs/ Li/Sr/Cs/Li/Sr/Cs/ Li/Sr/Cs/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Li/Sr/Zn/KLi/Sr/Zn/K/ Li/Sr/Zn/K/ Li/Sr/Zn/K/ Li/Sr/Zn/K/ Li/Sr/Zn/K/ Li/Sr/Zn/K/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Li/Ga/Cs Li/Ga/Cs/ Li/Ga/Cs/Li/Ga/Cs/ Li/Ga/Cs/ Li/Ga/Cs/ Li/Ga/Cs/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Li/K/Sr/La Li/K/Sr/La/ Li/K/Sr/La/ Li/K/Sr/La/Li/K/Sr/La/ Li/K/Sr/La/ Li/K/Sr/La/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Li/Na Li/Na/ Li/Na/ Li/Na/ Li/Na/ Li/Na/ Li/Na/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Li/Na/Rb/Ga Li/Na/Rb/Ga/Li/Na/Rb/Ga/ Li/Na/Rb/Ga/ Li/Na/Rb/Ga/ Li/Na/Rb/Ga/ Li/Na/Rb/Ga/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Li/Na/Sr Li/Na/Sr/ Li/Na/Sr/Li/Na/Sr/ Li/Na/Sr/ Li/Na/Sr/ Li/Na/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Li/Na/Sr/La Li/Na/Sr/La/ Li/Na/Sr/La/ Li/Na/Sr/La/Li/Na/Sr/La/ Li/Na/Sr/La/ Li/Na/Sr/La/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Li/Sm/Cs Li/Sm/Cs/ Li/Sm/Cs/ Li/Sm/Cs/ Li/Sm/Cs/Li/Sm/Cs/ Li/Sm/Cs/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ba/Sm/Yb/SBa/Sm/Yb/S/ Ba/Sm/Yb/S/ Ba/Sm/Yb/S/ Ba/Sm/Yb/S/ Ba/Sm/Yb/S/ Ba/Sm/Yb/S/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ba/Tm/K/La Ba/Tm/K/La/ Ba/Tm/K/La/Ba/Tm/K/La/ Ba/Tm/K/La/ Ba/Tm/K/La/ Ba/Tm/K/La/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Ba/Tm/Zn/K Ba/Tm/Zn/K/ Ba/Tm/Zn/K/ Ba/Tm/Zn/K/Ba/Tm/Zn/K/ Ba/Tm/Zn/K/ Ba/Tm/Zn/K/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Cs/K/La Cs/K/La/ Cs/K/La/ Cs/K/La/ Cs/K/La/ Cs/K/La/Cs/K/La/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Cs/La/Tm/Na Cs/La/Tm/Na/Cs/La/Tm/Na/ Cs/La/Tm/Na/ Cs/La/Tm/Na/ Cs/La/Tm/Na/ Cs/La/Tm/Na/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Cs/Li/K/La Cs/Li/K/La/ Cs/Li/K/La/Cs/Li/K/La/ Cs/Li/K/La/ Cs/Li/K/La/ Cs/Li/K/La/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sm/Li/Sr/Cs Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sr/Cs/La Sr/Cs/La/ Sr/Cs/La/ Sr/Cs/La/ Sr/Cs/La/Sr/Cs/La/ Sr/Cs/La/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/Tm/Li/CsSr/Tm/Li/Cs/ Sr/Tm/Li/Cs/ Sr/Tm/Li/Cs/ Sr/Tm/Li/Cs/ Sr/Tm/Li/Cs/Sr/Tm/Li/Cs/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Zn/K Zn/K/Zn/K/ Zn/K/ Zn/K/ Zn/K/ Zn/K/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Zr/Cs/K/La Zr/Cs/K/La/ Zr/Cs/K/La/ Zr/Cs/K/La/Zr/Cs/K/La/ Zr/Cs/K/La/ Zr/Cs/K/La/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Rb/Ca/In/Ni Rb/Ca/In/Ni/ Rb/Ca/In/Ni/ Rb/Ca/In/Ni/Rb/Ca/In/Ni/ Rb/Ca/In/Ni/ Rb/Ca/In/Ni/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sr/Ho/Tm Sr/Ho/Tm/ Sr/Ho/Tm/ Sr/Ho/Tm/ Sr/Ho/Tm/Sr/Ho/Tm/ Sr/Ho/Tm/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ La/Nd/SLa/Nd/S/ La/Nd/S/ La/Nd/S/ La/Nd/S/ La/Nd/S/ La/Nd/S/ La_(4-X)Nd_(X)O₆LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Li/Rb/Ca Li/Rb/Ca/ Li/Rb/Ca/ Li/Rb/Ca/ Li/Rb/Ca/Li/Rb/Ca/ Li/Rb/Ca/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Li/K Li/K/Li/K/ Li/K/ Li/K/ Li/K/ Li/K/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Tm/Lu/Ta/P Tm/Lu/Ta/P/ Tm/Lu/Ta/P/ Tm/Lu/Ta/P/Tm/Lu/Ta/P/ Tm/Lu/Ta/P/ Tm/Lu/Ta/P/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Rb/Ca/Dy/P Rb/Ca/Dy/P/ Rb/Ca/Dy/P/ Rb/Ca/Dy/P/Rb/Ca/Dy/P/ Rb/Ca/Dy/P/ Rb/Ca/Dy/P/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Mg/La/Yb/Zn Mg/La/Yb/Zn/ Mg/La/Yb/Zn/ Mg/La/Yb/Zn/Mg/La/Yb/Zn/ Mg/La/Yb/Zn/ Mg/La/Yb/Zn/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Rb/Sr/Lu Rb/Sr/Lu/ Rb/Sr/Lu/ Rb/Sr/Lu/ Rb/Sr/Lu/Rb/Sr/Lu/ Rb/Sr/Lu/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/Sr/Lu/NbNa/Sr/Lu/Nb/ Na/Sr/Lu/Nb/ Na/Sr/Lu/Nb/ Na/Sr/Lu/Nb/ Na/Sr/Lu/Nb/Na/Sr/Lu/Nb/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/Eu/HfNa/Eu/Hf/ Na/Eu/Hf/ Na/Eu/Hf/ Na/Eu/Hf/ Na/Eu/Hf/ Na/Eu/Hf/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Dy/Rb/Gd Dy/Rb/Gd/ Dy/Rb/Gd/Dy/Rb/Gd/ Dy/Rb/Gd/ Dy/Rb/Gd/ Dy/Rb/Gd/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Na/Pt/Bi Na/Pt/Bi/ Na/Pt/Bi/ Na/Pt/Bi/ Na/Pt/Bi/Na/Pt/Bi/ Na/Pt/Bi/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Rb/Hf Rb/Hf/Rb/Hf/ Rb/Hf/ Rb/Hf/ Rb/Hf/ Rb/Hf/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Ca/Cs Ca/Cs/ Ca/Cs/ Ca/Cs/ Ca/Cs/ Ca/Cs/ Ca/Cs/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ca/Mg/Na Ca/Mg/Na/ Ca/Mg/Na/Ca/Mg/Na/ Ca/Mg/Na/ Ca/Mg/Na/ Ca/Mg/Na/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Hf/Bi Hf/Bi/ Hf/Bi/ Hf/Bi/ Hf/Bi/ Hf/Bi/ Hf/Bi/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/Sn Sr/Sn/ Sr/Sn/ Sr/Sn/ Sr/Sn/Sr/Sn/ Sr/Sn/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/W Sr/W/Sr/W/ Sr/W/ Sr/W/ Sr/W/ Sr/W/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sr/Nb Sr/Nb/ Sr/Nb/ Sr/Nb/ Sr/Nb/ Sr/Nb/ Sr/Nb/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Zr/W Zr/W/ Zr/W/ Zr/W/ Zr/W/ Zr/W/Zr/W/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Y/W Y/W/ Y/W/ Y/W/ Y/W/ Y/W/ Y/W/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/W Na/W/ Na/W/ Na/W/ Na/W/ Na/W/Na/W/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Bi/W Bi/W/ Bi/W/ Bi/W/ Bi/W/ Bi/W/Bi/W/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Bi/Cs Bi/Cs/ Bi/Cs/ Bi/Cs/ Bi/Cs/Bi/Cs/ Bi/Cs/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Bi/Ca Bi/Ca/Bi/Ca/ Bi/Ca/ Bi/Ca/ Bi/Ca/ Bi/Ca/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Bi/Sn Bi/Sn/ Bi/Sn/ Bi/Sn/ Bi/Sn/ Bi/Sn/ Bi/Sn/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Bi/Sb Bi/Sb/ Bi/Sb/ Bi/Sb/ Bi/Sb/Bi/Sb/ Bi/Sb/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ge/Hf Ge/Hf/Ge/Hf/ Ge/Hf/ Ge/Hf/ Ge/Hf/ Ge/Hf/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Hf/Sm Hf/Sm/ Hf/Sm/ Hf/Sm/ Hf/Sm/ Hf/Sm/ Hf/Sm/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sb/Ag Sb/Ag/ Sb/Ag/ Sb/Ag/ Sb/Ag/Sb/Ag/ Sb/Ag/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sb/Bi Sb/Bi/Sb/Bi/ Sb/Bi/ Sb/Bi/ Sb/Bi/ Sb/Bi/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sb/Au Sb/Au/ Sb/Au/ Sb/Au/ Sb/Au/ Sb/Au/ Sb/Au/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sb/Sm Sb/Sm/ Sb/Sm/ Sb/Sm/ Sb/Sm/Sb/Sm/ Sb/Sm/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sb/Sr Sb/Sr/Sb/Sr/ Sb/Sr/ Sb/Sr/ Sb/Sr/ Sb/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sb/W Sb/W/ Sb/W/ Sb/W/ Sb/W/ Sb/W/ Sb/W/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sb/Hf Sb/Hf/ Sb/Hf/ Sb/Hf/ Sb/Hf/Sb/Hf/ Sb/Hf/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sb/Yb Sb/Yb/Sb/Yb/ Sb/Yb/ Sb/Yb/ Sb/Yb/ Sb/Yb/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sb/Sn Sb/Sn/ Sb/Sn/ Sb/Sn/ Sb/Sn/ Sb/Sn/ Sb/Sn/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Yb/Au Yb/Au/ Yb/Au/ Yb/Au/ Yb/Au/Yb/Au/ Yb/Au/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Yb/Ta Yb/Ta/Yb/Ta/ Yb/Ta/ Yb/Ta/ Yb/Ta/ Yb/Ta/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Yb/W Yb/W/ Yb/W/ Yb/W/ Yb/W/ Yb/W/ Yb/W/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Yb/Sr Yb/Sr/ Yb/Sr/ Yb/Sr/ Yb/Sr/Yb/Sr/ Yb/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Yb/Pb Yb/Pb/Yb/Pb/ Yb/Pb/ Yb/Pb/ Yb/Pb/ Yb/Pb/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Yb/W Yb/W/ Yb/W/ Yb/W/ Yb/W/ Yb/W/ Yb/W/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Yb/Ag Yb/Ag/ Yb/Ag/ Yb/Ag/ Yb/Ag/Yb/Ag/ Yb/Ag/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Au/Sr Au/Sr/Au/Sr/ Au/Sr/ Au/Sr/ Au/Sr/ Au/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ W/Ge W/Ge/ W/Ge/ W/Ge/ W/Ge/ W/Ge/ W/Ge/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ta/Sr Ta/Sr/ Ta/Sr/ Ta/Sr/ Ta/Sr/Ta/Sr/ Ta/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ta/Hf Ta/Hf/Ta/Hf/ Ta/Hf/ Ta/Hf/ Ta/Hf/ Ta/Hf/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ W/Au W/Au/ W/Au/ W/Au/ W/Au/ W/Au/ W/Au/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ca/W Ca/W/ Ca/W/ Ca/W/ Ca/W/ Ca/W/Ca/W/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Au/Re Au/Re/ Au/Re/ Au/Re/ Au/Re/Au/Re/ Au/Re/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sm/Li Sm/Li/Sm/Li/ Sm/Li/ Sm/Li/ Sm/Li/ Sm/Li/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ La/K La/K/ La/K/ La/K/ La/K/ La/K/ La/K/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Zn/Cs Zn/Cs/ Zn/Cs/ Zn/Cs/ Zn/Cs/Zn/Cs/ Zn/Cs/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/K/MgNa/K/Mg/ Na/K/Mg/ Na/K/Mg/ Na/K/Mg/ Na/K/Mg/ Na/K/Mg/ La_(4-X)Nd_(X)O₆LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Zr/Cs Zr/Cs/ Zr/Cs/ Zr/Cs/ Zr/Cs/ Zr/Cs/ Zr/Cs/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ca/Ce Ca/Ce/ Ca/Ce/ Ca/Ce/ Ca/Ce/Ca/Ce/ Ca/Ce/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/Li/CsNa/Li/Cs/ Na/Li/Cs/ Na/Li/Cs/ Na/Li/Cs/ Na/Li/Cs/ Na/Li/Cs/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Li/Sr Li/Sr/ Li/Sr/ Li/Sr/ Li/Sr/Li/Sr/ Li/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ La/Dy/KLa/Dy/K/ La/Dy/K/ La/Dy/K/ La/Dy/K/ La/Dy/K/ La/Dy/K/ La_(4-X)Nd_(X)O₆LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Dy/K Dy/K/ Dy/K/ Dy/K/ Dy/K/ Dy/K/ Dy/K/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ La/Mg La/Mg/ La/Mg/ La/Mg/ La/Mg/La/Mg/ La/Mg/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/Nd/In/KNa/Nd/In/K/ Na/Nd/In/K/ Na/Nd/In/K/ Na/Nd/In/K/ Na/Nd/In/K/ Na/Nd/In/K/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ In/Sr In/Sr/ In/Sr/ In/Sr/ In/Sr/In/Sr/ In/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/Cs Sr/Cs/Sr/Cs/ Sr/Cs/ Sr/Cs/ Sr/Cs/ Sr/Cs/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Rb/Ga/Tm/Cs Rb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/Rb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Ga/Cs Ga/Cs/ Ga/Cs/ Ga/Cs/ Ga/Cs/ Ga/Cs/ Ga/Cs/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ K/La/Zr/Ag K/La/Zr/Ag/ K/La/Zr/Ag/K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Lu/Fe Lu/Fe/ Lu/Fe/ Lu/Fe/ Lu/Fe/ Lu/Fe/ Lu/Fe/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/Tm Sr/Tm/ Sr/Tm/ Sr/Tm/ Sr/Tm/Sr/Tm/ Sr/Tm/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ La/Dy La/Dy/La/Dy/ La/Dy/ La/Dy/ La/Dy/ La/Dy/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sm/Li/Sr Sm/Li/Sr/ Sm/Li/Sr/ Sm/Li/Sr/ Sm/Li/Sr/Sm/Li/Sr/ Sm/Li/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Mg/K Mg/K/Mg/K/ Mg/K/ Mg/K/ Mg/K/ Mg/K/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Li/Rb/Ga Li/Rb/Ga/ Li/Rb/Ga/ Li/Rb/Ga/ Li/Rb/Ga/Li/Rb/Ga/ Li/Rb/Ga/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Li/Cs/TmLi/Cs/Tm/ Li/Cs/Tm/ Li/Cs/Tm/ Li/Cs/Tm/ Li/Cs/Tm/ Li/Cs/Tm/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Zr/K Zr/K/ Zr/K/ Zr/K/ Zr/K/ Zr/K/Zr/K/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Li/Cs Li/Cs/ Li/Cs/ Li/Cs/ Li/Cs/Li/Cs/ Li/Cs/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Li/K/LaLi/K/La/ Li/K/La/ Li/K/La/ Li/K/La/ Li/K/La/ Li/K/La/ La_(4-X)Nd_(X)O₆LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Ce/Zr/La Ce/Zr/La/ Ce/Zr/La/ Ce/Zr/La/ Ce/Zr/La/Ce/Zr/La/ Ce/Zr/La/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ca/Al/LaCa/Al/La/ Ca/Al/La/ Ca/Al/La/ Ca/Al/La/ Ca/Al/La/ Ca/Al/La/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/Zn/La Sr/Zn/La/ Sr/Zn/La/Sr/Zn/La/ Sr/Zn/La/ Sr/Zn/La/ Sr/Zn/La/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sr/Cs/Zn Sr/Cs/Zn/ Sr/Cs/Zn/ Sr/Cs/Zn/ Sr/Cs/Zn/Sr/Cs/Zn/ Sr/Cs/Zn/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sm/Cs Sm/Cs/Sm/Cs/ Sm/Cs/ Sm/Cs/ Sm/Cs/ Sm/Cs/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ In/K In/K/ In/K/ In/K/ In/K/ In/K/ In/K/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ho/Cs/Li/La Ho/Cs/Li/La/Ho/Cs/Li/La/ Ho/Cs/Li/La/ Ho/Cs/Li/La/ Ho/Cs/Li/La/ Ho/Cs/Li/La/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Cs/La/Na Cs/La/Na/ Cs/La/Na/Cs/La/Na/ Cs/La/Na/ Cs/La/Na/ Cs/La/Na/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ La/S/Sr La/S/Sr/ La/S/Sr/ La/S/Sr/ La/S/Sr/ La/S/Sr/La/S/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ K/La/Zr/Ag K/La/Zr/Ag/ K/La/Zr/Ag/K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Lu/Tl Lu/Tl/ Lu/Tl/ Lu/Tl/ Lu/Tl/ Lu/Tl/ Lu/Tl/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Pr/Zn Pr/Zn/ Pr/Zn/ Pr/Zn/ Pr/Zn/Pr/Zn/ Pr/Zn/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Rb/Sr/LaRb/Sr/La/ Rb/Sr/La/ Rb/Sr/La/ Rb/Sr/La/ Rb/Sr/La/ Rb/Sr/La/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/Sr/Eu/Ca Na/Sr/Eu/Ca/Na/Sr/Eu/Ca/ Na/Sr/Eu/Ca/ Na/Sr/Eu/Ca/ Na/Sr/Eu/Ca/ Na/Sr/Eu/Ca/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ K/Cs/Sr/La K/Cs/Sr/La/ K/Cs/Sr/La/K/Cs/Sr/La/ K/Cs/Sr/La/ K/Cs/Sr/La/ K/Cs/Sr/La/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Na/Sr/Lu Na/Sr/Lu/ Na/Sr/Lu/ Na/Sr/Lu/ Na/Sr/Lu/Na/Sr/Lu/ Na/Sr/Lu/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/Eu/DySr/Eu/Dy/ Sr/Eu/Dy/ Sr/Eu/Dy/ Sr/Eu/Dy/ Sr/Eu/Dy/ Sr/Eu/Dy/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Lu/Nb Lu/Nb/ Lu/Nb/ Lu/Nb/ Lu/Nb/Lu/Nb/ Lu/Nb/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ La/Dy/GdLa/Dy/Gd/ La/Dy/Gd/ La/Dy/Gd/ La/Dy/Gd/ La/Dy/Gd/ La/Dy/Gd/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/Mg/Tl/P Na/Mg/Tl/P/ Na/Mg/Tl/P/Na/Mg/Tl/P/ Na/Mg/Tl/P/ Na/Mg/Tl/P/ Na/Mg/Tl/P/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Na/Pt Na/Pt/ Na/Pt/ Na/Pt/ Na/Pt/ Na/Pt/ Na/Pt/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Gd/Li/K Gd/Li/K/ Gd/Li/K/ Gd/Li/K/Gd/Li/K/ Gd/Li/K/ Gd/Li/K/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Rb/K/LuRb/K/Lu/ Rb/K/Lu/ Rb/K/Lu/ Rb/K/Lu/ Rb/K/Lu/ Rb/K/Lu/ La_(4-X)Nd_(X)O₆LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sr/La/Dy/S Sr/La/Dy/S/ Sr/La/Dy/S/ Sr/La/Dy/S/Sr/La/Dy/S/ Sr/La/Dy/S/ Sr/La/Dy/S/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Na/Ce/Co Na/Ce/Co/ Na/Ce/Co/ Na/Ce/Co/ Na/Ce/Co/Na/Ce/Co/ Na/Ce/Co/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na/Ce Na/Ce/Na/Ce/ Na/Ce/ Na/Ce/ Na/Ce/ Na/Ce/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Na/Ga/Gd/Al Na/Ga/Gd/Al/ Na/Ga/Gd/Al/ Na/Ga/Gd/Al/Na/Ga/Gd/Al/ Na/Ga/Gd/Al/ Na/Ga/Gd/Al/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Ba/Rh/Ta Ba/Rh/Ta/ Ba/Rh/Ta/ Ba/Rh/Ta/ Ba/Rh/Ta/Ba/Rh/Ta/ Ba/Rh/Ta/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ba/Ta Ba/Ta/Ba/Ta/ Ba/Ta/ Ba/Ta/ Ba/Ta/ Ba/Ta/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Na/Al/Bi Na/Al/Bi/ Na/Al/Bi/ Na/Al/Bi/ Na/Al/Bi/Na/Al/Bi/ Na/Al/Bi/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Cs/Eu/SCs/Eu/S/ Cs/Eu/S/ Cs/Eu/S/ Cs/Eu/S/ Cs/Eu/S/ Cs/Eu/S/ La_(4-X)Nd_(X)O₆LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sm/Tm/Yb/Fe Sm/Tm/Yb/Fe/ Sm/Tm/Yb/Fe/ Sm/Tm/Yb/Fe/Sm/Tm/Yb/Fe/ Sm/Tm/Yb/Fe/ Sm/Tm/Yb/Fe/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sm/Tm/Yb Sm/Tm/Yb/ Sm/Tm/Yb/ Sm/Tm/Yb/ Sm/Tm/Yb/Sm/Tm/Yb/ Sm/Tm/Yb/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Hf/Zr/TaHf/Zr/Ta/ Hf/Zr/Ta/ Hf/Zr/Ta/ Hf/Zr/Ta/ Hf/Zr/Ta/ Hf/Zr/Ta/ Rb/Gd/Li/KRb/Gd/Li/K/ Rb/Gd/Li/K/ Rb/Gd/Li/K/ Rb/Gd/Li/K/ Rb/Gd/Li/K/ Rb/Gd/Li/K/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Gd/Ho/Al/P Gd/Ho/Al/P/ Gd/Ho/Al/P/Gd/Ho/Al/P/ Gd/Ho/Al/P/ Gd/Ho/Al/P/ Gd/Ho/Al/P/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Na/Ca/Lu Na/Ca/Lu/ Na/Ca/Lu/ Na/Ca/Lu/ Na/Ca/Lu/Na/Ca/Lu/ Na/Ca/Lu/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Cu/Sn Cu/Sn/Cu/Sn/ Cu/Sn/ Cu/Sn/ Cu/Sn/ Cu/Sn/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Ag/Au Ag/Au/ Ag/Au/ Ag/Au/ Ag/Au/ Ag/Au/ Ag/Au/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Al/Bi Al/Bi/ Al/Bi/ Al/Bi/ Al/Bi/Al/Bi/ Al/Bi/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Al/Mo Al/Mo/Al/Mo/ Al/Mo/ Al/Mo/ Al/Mo/ Al/Mo/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Al/Nb Al/Nb/ Al/Nb/ Al/Nb/ Al/Nb/ Al/Nb/ Al/Nb/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Au/Pt Au/Pt/ Au/Pt/ Au/Pt/ Au/Pt/Au/Pt/ Au/Pt/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ga/Bi Ga/Bi/Ga/Bi/ Ga/Bi/ Ga/Bi/ Ga/Bi/ Ga/Bi/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Mg/W Mg/W/ Mg/W/ Mg/W/ Mg/W/ Mg/W/ Mg/W/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Pb/Au Pb/Au/ Pb/Au/ Pb/Au/ Pb/Au/Pb/Au/ Pb/Au/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sn/Mg Sn/Mg/Sn/Mg/ Sn/Mg/ Sn/Mg/ Sn/Mg/ Sn/Mg/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Zn/Bi Zn/Bi/ Zn/Bi/ Zn/Bi/ Zn/Bi/ Zn/Bi/ Zn/Bi/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/Ta Sr/Ta/ Sr/Ta/ Sr/Ta/ Sr/Ta/Sr/Ta/ Sr/Ta/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Na Na/ Na/ Na/Na/ Na/ Na/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr Sr/ Sr/ Sr/Sr/ Sr/ Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ca Ca/ Ca/ Ca/Ca/ Ca/ Ca/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Yb Yb/ Yb/ Yb/Yb/ Yb/ Yb/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Cs Cs/ Cs/ Cs/Cs/ Cs/ Cs/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sb Sb/ Sb/ Sb/Sb/ Sb/ Sb/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Gd/Ho Gd/Ho/Gd/Ho/ Gd/Ho/ Gd/Ho/ Gd/Ho/ Gd/Ho/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Zr/Bi Zr/Bi/ Zr/Bi/ Zr/Bi/ Zr/Bi/ Zr/Bi/ Zr/Bi/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ho/Sr Ho/Sr/ Ho/Sr/ Ho/Sr/ Ho/Sr/Ho/Sr/ Ho/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Gd/Ho/SrGd/Ho/Sr/ Gd/Ho/Sr/ Gd/Ho/Sr/ Gd/Ho/Sr/ Gd/Ho/Sr/ Gd/Ho/Sr/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ca/Sr Ca/Sr/ Ca/Sr/ Ca/Sr/ Ca/Sr/Ca/Sr/ Ca/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ca/Sr/WCa/Sr/W/ Ca/Sr/W/ Ca/Sr/VV/ Ca/Sr/W/ Ca/Sr/W/ Ca/Sr/VV/ La_(4-X)Nd_(X)O₆LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Na/Zr/Eu/Tm Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sr/Ho/Tm/Na Sr/Ho/Tm/Na/ Sr/Ho/Tm/Na/ Sr/Ho/Tm/Na/Sr/Ho/Tm/Na/ Sr/Ho/Tm/Na/ Sr/Ho/Tm/Na/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sr/Pb Sr/Pb/ Sr/Pb/ Sr/Pb/ Sr/Pb/ Sr/Pb/ Sr/Pb/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/W/Li Sr/W/Li/ Sr/W/Li/ Sr/W/Li/Sr/W/Li/ Sr/W/Li/ Sr/W/Li/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ca/Sr/WCa/Sr/W/ Ca/Sr/W/ Ca/Sr/VV/ Ca/Sr/W/ Ca/Sr/W/ Ca/Sr/VV/ La_(4-X)Nd_(X)O₆LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Sr/Hf Sr/Hf/ Sr/Hf/ Sr/Hf/ Sr/Hf/ Sr/Hf/ Sr/Hf/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Au/Re Au/Re/ Au/Re/ Au/Re/ Au/Re/Au/Re/ Au/Re/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/W Sr/W/Sr/W/ Sr/W/ Sr/W/ Sr/W/ Sr/W/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ La/Nd La/Nd/ La/Nd/ La/Nd/ La/Nd/ La/Nd/ La/Nd/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ La/Sm La/Sm/ La/Sm/ La/Sm/ La/Sm/La/Sm/ La/Sm/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ La/Ce La/Ce/La/Ce/ La/Ce/ La/Ce/ La/Ce/ La/Ce/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ La/Sr La/Sr/ La/Sr/ La/Sr/ La/Sr/ La/Sr/ La/Sr/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ La/Nd/Sr La/Nd/Sr/ La/Nd/Sr/La/Nd/Sr/ La/Nd/Sr/ La/Nd/Sr/ La/Nd/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ La/Bi/Sr La/Bi/Sr/ La/Bi/Sr/ La/Bi/Sr/ La/Bi/Sr/La/Bi/Sr/ La/Bi/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ La/Ce/Nd/SrLa/Ce/Nd/Sr/ La/Ce/Nd/Sr/ La/Ce/Nd/Sr/ La/Ce/Nd/Sr/ La/Ce/Nd/Sr/La/Ce/Nd/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ La/Bi/Ce/Nd/La/Bi/Ce/Nd/Sr/ La/Bi/Ce/Nd/Sr/ La/Bi/Ce/Nd/Sr/ La/Bi/Ce/Nd/Sr/La/Bi/Ce/Nd/Sr/ La/Bi/Ce/Nd/Sr/ Sr La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Eu/Gd Eu/Gd/ Eu/Gd/ Eu/Gd/ Eu/Gd/ Eu/Gd/ Eu/Gd/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ca/Na Ca/Na/ Ca/Na/ Ca/Na/ Ca/Na/Ca/Na/ Ca/Na/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Eu/Sm Eu/Sm/Eu/Sm/ Eu/Sm/ Eu/Sm/ Eu/Sm/ Eu/Sm/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Eu/Sr Eu/Sr/ Eu/Sr/ Eu/Sr/ Eu/Sr/ Eu/Sr/ Eu/Sr/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Mg/Sr Mg/Sr/ Mg/Sr/ Mg/Sr/ Mg/Sr/Mg/Sr/ Mg/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Ce/Mg Ce/Mg/Ce/Mg/ Ce/Mg/ Ce/Mg/ Ce/Mg/ Ce/Mg/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Gd/Sm Gd/Sm/ Gd/Sm/ Gd/Sm/ Gd/Sm/ Gd/Sm/ Gd/Sm/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Au/Pb Au/Pb/ Au/Pb/ Au/Pb/ Au/Pb/Au/Pb/ Au/Pb/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Bi/Hf Bi/Hf/Bi/Hf/ Bi/Hf/ Bi/Hf/ Bi/Hf/ Bi/Hf/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Rb/S Rb/S/ Rb/S/ Rb/S/ Rb/S/ Rb/S/ Rb/S/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Sr/Nd Sr/Nd/ Sr/Nd/ Sr/Nd/ Sr/Nd/Sr/Nd/ Sr/Nd/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Eu/Y Eu/Y/Eu/Y/ Eu/Y/ Eu/Y/ Eu/Y/ Eu/Y/ La_(4-X)Nd_(X)O₆ LaNd₃O₆La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆La_(3.5)Nd_(0.5)O₆ Mg/Nd Mg/Nd/ Mg/Nd/ Mg/Nd/ Mg/Nd/ Mg/Nd/ Mg/Nd/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ La/Mg La/Mg/ La/Mg/ La/Mg/ La/Mg/La/Mg/ La/Mg/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Mg/Nd/FeMg/Nd/Fe/ Mg/Nd/Fe/ Mg/Nd/Fe/ Mg/Nd/Fe/ Mg/Nd/Fe/ Mg/Nd/Fe/La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆ La_(2.5)Nd_(1.5)O₆La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆ Rb/Sr Rb/Sr/ Rb/Sr/ Rb/Sr/ Rb/Sr/Rb/Sr/ Rb/Sr/ La_(4-X)Nd_(X)O₆ LaNd₃O₆ La_(1.5)Nd_(2.5)O₆La_(2.5)Nd_(1.5)O₆ La_(3.2)Nd_(0.8)O₆ La_(3.5)Nd_(0.5)O₆

TABLE 3 CATALYSTS (CAT) DOPED WITH SPECIFIC DOPANTS (DOP) Dop\CatLa_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Eu/Na Eu/Na/ Eu/Na/ Eu/Na/Eu/Na/ Eu/Na/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sr/Na Sr/Na/Sr/Na/ Sr/Na/ Sr/Na/ Sr/Na/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaNa/Zr/Eu/Ca Na/Zr/Eu/Ca/ Na/Zr/Eu/Ca/ Na/Zr/Eu/Ca/ Na/Zr/Eu/Ca/Na/Zr/Eu/Ca/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-Laa Ce-La Mg/Na Mg/Na/Mg/Na/ Mg/Na/ Mg/Na/ Mg/Na/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaSr/Sm/Ho/Tm Sr/Sm/Ho/Tm/ Sr/Sm/Ho/Tm/ Sr/Sm/Ho/Tm/ Sr/Sm/Ho/Tm/Sr/Sm/Ho/Tm/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sr/W Sr/W/ Sr/W/Sr/W/ Sr/W/ Sr/W/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Mg/La/KMg/La/K/ Mg/La/K/ Mg/La/K/ Mg/La/K/ Mg/La/K/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Na/K/Mg/Tm Na/K/Mg/Tm/ Na/K/Mg/Tm/ Na/K/Mg/Tm/Na/K/Mg/Tm/ Na/K/Mg/Tm/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaNa/Dy/K Na/Dy/K/ Na/Dy/K/ Na/Dy/K/ Na/Dy/K/ Na/Dy/K/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Na/La/Dy Na/La/Dy/ Na/La/Dy/ Na/La/Dy/ Na/La/Dy/Na/La/Dy/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Na/La/Eu Na/La/Eu/Na/La/Eu/ Na/La/Eu/ Na/La/Eu/ Na/La/Eu/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Na/La/Eu/In Na/La/Eu/In/ Na/La/Eu/In/ Na/La/Eu/In/Na/La/Eu/In/ Na/La/Eu/In/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaNa/La/K Na/La/K/ Na/La/K/ Na/La/K/ Na/La/K/ Na/La/K/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Na/La/Li/Cs Na/La/Li/Cs/ Na/La/Li/Cs/Na/La/Li/Cs/ Na/La/Li/Cs/ Na/La/Li/Cs/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La K/La K/La/ K/La/ K/La/ K/La/ K/La/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La K/La/S K/La/S/ K/La/S/ K/La/S/ K/La/S/ K/La/S/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La K/Na K/Na/ K/Na/ K/Na/ K/Na/K/Na/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Li/Cs Li/Cs/ Li/Cs/Li/Cs/ Li/Cs/ Li/Cs/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Li/Cs/LaLi/Cs/La/ Li/Cs/La/ Li/Cs/La/ Li/Cs/La/ Li/Cs/La/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Li/Cs/La/Tm Li/Cs/La/Tm/ Li/Cs/La/Tm/Li/Cs/La/Tm/ Li/Cs/La/Tm/ Li/Cs/La/Tm/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Li/Cs/Sr/Tm Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaLi/Sr/Cs Li/Sr/Cs/ Li/Sr/Cs/ Li/Sr/Cs/ Li/Sr/Cs/ Li/Sr/Cs/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Li/Sr/Zn/K Li/Sr/Zn/K/Li/Sr/Zn/K/ Li/Sr/Zn/K/ Li/Sr/Zn/K/ Li/Sr/Zn/K/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Li/Ga/Cs Li/Ga/Cs/ Li/Ga/Cs/ Li/Ga/Cs/ Li/Ga/Cs/Li/Ga/Cs/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Li/K/Sr/LaLi/K/Sr/La/ Li/K/Sr/La/ Li/K/Sr/La/ Li/K/Sr/La/ Li/K/Sr/La/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Li/Na Li/Na/ Li/Na/ Li/Na/Li/Na/ Li/Na/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Li/Na/Rb/GaLi/Na/Rb/Ga/ Li/Na/Rb/Ga/ Li/Na/Rb/Ga/ Li/Na/Rb/Ga/ Li/Na/Rb/Ga/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Li/Na/Sr Li/Na/Sr/ Li/Na/Sr/Li/Na/Sr/ Li/Na/Sr/ Li/Na/Sr/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaLi/Na/Sr/La Li/Na/Sr/La/ Li/Na/Sr/La/ Li/Na/Sr/La/ Li/Na/Sr/La/Li/Na/Sr/La/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Li/Sm/CsLi/Sm/Cs/ Li/Sm/Cs/ Li/Sm/Cs/ Li/Sm/Cs/ Li/Sm/Cs/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Ba/Sm/Yb/S Ba/Sm/Yb/S/ Ba/Sm/Yb/S/ Ba/Sm/Yb/S/Ba/Sm/Yb/S/ Ba/Sm/Yb/S/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaBa/Tm/K/La Ba/Tm/K/La/ Ba/Tm/K/La/ Ba/Tm/K/La/ Ba/Tm/K/La/ Ba/Tm/K/La/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Ba/Tm/Zn/K Ba/Tm/Zn/K/Ba/Tm/Zn/K/ Ba/Tm/Zn/K/ Ba/Tm/Zn/K/ Ba/Tm/Zn/K/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La C+s/K/La Cs/K/La/ Cs/K/La/ Cs/K/La/ Cs/K/La/ Cs/K/La/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Cs/La/Tm/Na Cs/La/Tm/Na/Cs/La/Tm/Na/ Cs/La/Tm/Na/ Cs/La/Tm/Na/ C/s/La/Tm/Na La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Cs/Li/K/La Cs/Li/K/La/ Cs/Li/K/La/ Cs/Li/K/La/Cs/Li/K/La/ Cs/Li/K/La/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaSm/Li/Sr/Cs Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/Sm/Li/Sr/Cs/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sr/Cs/LaSr/Cs/La/ Sr/Cs/La/ Sr/Cs/La/ Sr/Cs/La/ Sr/Cs/La/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Sr/Tm/Li/Cs Sr/Tm/Li/Cs/ Sr/Tm/Li/Cs/Sr/Tm/Li/Cs/ Sr/Tm/Li/Cs/ Sr/Tm/Li/Cs/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Zn/K Zn/K/ Zn/K/ Zn/K/ Zn/K/ Zn/K/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Zr/Cs/K/La Zr/Cs/K/La/ Zr/Cs/K/La/ Zr/Cs/K/La/Zr/Cs/K/La/ Zr/Cs/K/La/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaRb/Ca/In/Ni Rb/Ca/In/Ni/ Rb/Ca/In/Ni/ Rb/Ca/In/Ni/ Rb/Ca/In/Ni/Rb/Ca/In/Ni/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sr/Ho/TmSr/Ho/Tm/ Sr/Ho/Tm/ Sr/Ho/Tm/ Sr/Ho/Tm/ Sr/Ho/Tm/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La La/Nd/S La/Nd/S/ La/Nd/S/ La/Nd/S/ La/Nd/S/La/Nd/S/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Li/Rb/Ca Li/Rb/Ca/Li/Rb/Ca/ Li/Rb/Ca/ Li/Rb/Ca/ Li/Rb/Ca/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Li/K Li/K/ Li/K/ Li/K/ Li/K/ Li/K/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Tm/Lu/Ta/P Tm/Lu/Ta/P/ Tm/Lu/Ta/P/ Tm/Lu/Ta/P/Tm/Lu/Ta/P/ Tm/Lu/Ta/P/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaRb/Ca/Dy/P Rb/Ca/Dy/P/ Rb/Ca/Dy/P/ Rb/Ca/Dy/P/ Rb/Ca/Dy/P/ Rb/Ca/Dy/P/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Mg/La/Yb/Zn Mg/La/Yb/Zn/Mg/La/Yb/Zn/ Mg/La/Yb/Zn/ Mg/La/Yb/Zn/ Mg/La/Yb/Zn/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Rb/Sr/Lu Rb/Sr/Lu/ Rb/Sr/Lu/ Rb/Sr/Lu/ Rb/Sr/Lu/Rb/Sr/Lu/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Na/Sr/Lu/NbNa/Sr/Lu/Nb/ Na/Sr/Lu/Nb/ Na/Sr/Lu/Nb/ Na/Sr/Lu/Nb/ Na/Sr/Lu/Nb/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Na/Eu/Hf Na/Eu/Hf/ Na/Eu/Hf/Na/Eu/Hf/ Na/Eu/Hf/ Na/Eu/Hf/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaDy/Rb/Gd Dy/Rb/Gd/ Dy/Rb/Gd/ Dy/Rb/Gd/ Dy/Rb/Gd/ Dy/Rb/Gd/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Na/Pt/Bi Na/Pt/Bi/ Na/Pt/Bi/Na/Pt/Bi/ Na/Pt/Bi/ Na/Pt/Bi/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaRb/Hf Rb/Hf/ Rb/Hf/ Rb/Hf/ Rb/Hf/ Rb/Hf/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Ca/Cs Ca/Cs/ Ca/Cs/ Ca/Cs/ Ca/Cs/ Ca/Cs/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Ca/Mg/Na Ca/Mg/Na/ Ca/Mg/Na/ Ca/Mg/Na/ Ca/Mg/Na/Ca/Mg/Na/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Hf/Bi Hf/Bi/ Hf/Bi/Hf/Bi/ Hf/Bi/ Hf/Bi/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sr/SnSr/Sn/ Sr/Sn/ Sr/Sn/ Sr/Sn/ Sr/Sn/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-LaCe-La Sr/W Sr/W/ Sr/W/ Sr/W/ Sr/W/ Sr/W/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Sr/Nb Sr/Nb/ Sr/Nb/ Sr/Nb/ Sr/Nb/ Sr/Nb/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Zr/W Zr/W/ Zr/W/ Zr/W/ Zr/W/ Zr/W/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Y/W Y/W/ Y/W/ Y/W/ Y/W/ Y/W/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Na/W Na/W/ Na/W/ Na/W/ Na/W/Na/W/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Bi/W Bi/W/ Bi/W/ Bi/W/Bi/W/ Bi/W/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Bi/Cs Bi/Cs/Bi/Cs/ Bi/Cs/ Bi/Cs/ Bi/Cs/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaBi/Ca Bi/Ca/ Bi/Ca/ Bi/Ca/ Bi/Ca/ Bi/Ca/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Bi/Sn Bi/Sn/ Bi/Sn/ Bi/Sn/ Bi/Sn/ Bi/Sn/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Bi/Sb Bi/Sb/ Bi/Sb/ Bi/Sb/ Bi/Sb/ Bi/Sb/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Ge/Hf Ge/Hf/ Ge/Hf/ Ge/Hf/Ge/Hf/ Ge/Hf/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Hf/Sm Hf/Sm/Hf/Sm/ Hf/Sm/ Hf/Sm/ Hf/Sm/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaSb/Ag Sb/Ag/ Sb/Ag/ Sb/Ag/ Sb/Ag/ Sb/Ag/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Sb/Bi Sb/Bi/ Sb/Bi/ Sb/Bi/ Sb/Bi/ Sb/Bi/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Sb/Au Sb/Au/ Sb/Au/ Sb/Au/ Sb/Au/ Sb/Au/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sb/Sm Sb/Sm/ Sb/Sm/ Sb/Sm/Sb/Sm/ Sb/Sm/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sb/Sr Sb/Sr/Sb/Sr/ Sb/Sr/ Sb/Sr/ Sb/Sr/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaSb/W Sb/W/ Sb/W/ Sb/W/ Sb/W/ Sb/W/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-LaCe-La Sb/Hf Sb/Hf/ Sb/Hf/ Sb/Hf/ Sb/Hf/ Sb/Hf/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Sb/Yb Sb/Yb/ Sb/Yb/ Sb/Yb/ Sb/Yb/ Sb/Yb/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sb/Sn Sb/Sn/ Sb/Sn/ Sb/Sn/Sb/Sn/ Sb/Sn/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Yb/Au Yb/Au/Yb/Au/ Yb/Au/ Yb/Au/ Yb/Au/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaYb/Ta Yb/Ta/ Yb/Ta/ Yb/Ta/ Yb/Ta/ Yb/Ta/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Yb/W Yb/W/ Yb/W/ Yb/W/ Yb/W/ Yb/W/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Yb/Sr Yb/Sr/ Yb/Sr/ Yb/Sr/ Yb/Sr/ Yb/Sr/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Yb/Pb Yb/Pb/ Yb/Pb/ Yb/Pb/Yb/Pb/ Yb/Pb/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Yb/W Yb/W/ Yb/W/Yb/W/ Yb/W/ Yb/W/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Yb/Ag Yb/Ag/Yb/Ag/ Yb/Ag/ Yb/Ag/ Yb/Ag/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaAu/Sr Au/Sr/ Au/Sr/ Au/Sr/ Au/Sr/ Au/Sr La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La W/Ge W/Ge/ W/Ge/ W/Ge/ W/Ge/ W/Ge/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Ta/Sr Ta/Sr/ Ta/Sr/ Ta/Sr/ Ta/Sr/ Ta/Sr/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Ta/Hf Ta/Hf/ Ta/Hf/ Ta/Hf/Ta/Hf/ Ta/Hf/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La W/Au W/Au/ W/Au/W/Au/ W/Au/ W/Au/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Ca/W Ca/W/Ca/W/ Ca/W/ Ca/W/ Ca/W/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Au/ReAu/Re/ Au/Re/ Au/Re/ Au/Re/ Au/Re/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-LaCe-La Sm/Li Sm/Li/ Sm/Li/ Sm/Li/ Sm/Li/ Sm/Li/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La La/K La/K/ La/K/ La/K/ La/K/ La/K/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Zn/Cs Zn/Cs/ Zn/Cs/ Zn/Cs/ Zn/Cs/ Zn/Cs/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Na/K/Mg Na/K/Mg/ Na/K/Mg/Na/K/Mg/ Na/K/Mg/ Na/K/Mg/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaZr/Cs Zr/Cs/ Zr/Cs/ Zr/Cs/ Zr/Cs/ Zr/Cs/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Ca/Ce Ca/Ce/ Ca/Ce/ Ca/Ce/ Ca/Ce/ Ca/Ce/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Na/Li/Cs Na/Li/Cs/ Na/Li/Cs/ Na/Li/Cs/ Na/Li/Cs/Na/Li/Cs La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Li/Sr Li/Sr/ Li/Sr/Li/Sr/ Li/Sr/ Li/Sr/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La La/Dy/KLa/Dy/K/ La/Dy/K/ La/Dy/K/ La/Dy/K/ La/Dy/K/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Dy/K Dy/K/ Dy/K/ Dy/K/ Dy/K/ Dy/K/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La La/Mg La/Mg/ La/Mg/ La/Mg/ La/Mg/ La/Mg/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Na/Nd/In/K Na/Nd/In/K/Na/Nd/In/K/ Na/Nd/In/K/ Na/Nd/In/K/ Na/Nd/In/K/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La In/Sr In/Sr/ In/Sr/ In/Sr/ In/Sr/ In/Sr/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sr/Cs Sr/Cs/ Sr/Cs/ Sr/Cs/Sr/Cs/ Sr/Cs/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Rb/Ga/Tm/CsRb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Ga/Cs Ga/Cs/ Ga/Cs/ Ga/Cs/Ga/Cs/ Ga/Cs/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La K/La/Zr/AgK/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Lu/Fe Lu/Fe/ Lu/Fe/ Lu/Fe/Lu/Fe/ Lu/Fe/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sr/Tm Sr/Tm/Sr/Tm/ Sr/Tm/ Sr/Tm/ Sr/Tm/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaLa/Dy La/Dy/ La/Dy/ La/Dy/ La/Dy/ La/Dy/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Sm/Li/Sr Sm/Li/Sr/ Sm/Li/Sr/ Sm/Li/Sr/ Sm/Li/Sr/ Sm/Li/Sr/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Mg/K Mg/K/ Mg/K/ Mg/K/ Mg/K/Mg/K/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Li/Rb/Ga Li/Rb/Ga/Li/Rb/Ga/ Li/Rb/Ga/ Li/Rb/Ga/ Li/Rb/Ga/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Li/Cs/Tm Li/Cs/Tm/ Li/Cs/Tm/ Li/Cs/Tm/ Li/Cs/Tm/ Li/Cs/Tm/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Zr/K Zr/K/ Zr/K/ Zr/K/ Zr/K/Zr/K/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Li/Cs Li/Cs/ Li/Cs/Li/Cs/ Li/Cs/ Li/Cs/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Li/K/LaLi/K/La/ Li/K/La/ Li/K/La/ Li/K/La/ Li/K/La/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Ce/Zr/La Ce/Zr/La/ Ce/Zr/La/ Ce/Zr/La/ Ce/Zr/La/Ce/Zr/La/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Ca/Al/La Ca/Al/La/Ca/Al/La/ Ca/Al/La/ Ca/Al/La/ Ca/Al/La/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Sr/Zn/La Sr/Zn/La/ Sr/Zn/La/ Sr/Zn/La/ Sr/Zn/La/ Sr/Zn/La/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sr/Cs/Zn Sr/Cs/Zn/ Sr/Cs/Zn/Sr/Cs/Zn/ Sr/Cs/Zn/ Sr/Cs/Zn La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaSm/Cs Sm/Cs/ Sm/Cs/ Sm/Cs/ Sm/Cs/ Sm/Cs La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La In/K In/K/ In/K/ In/K/ In/K/ In/K/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Ho/Cs/Li/La Ho/Cs/Li/La/ Ho/Cs/Li/La/ Ho/Cs/Li/La/Ho/Cs/Li/La/ Ho/Cs/Li/La/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaCs/La/Na Cs/La/Na/ Cs/La/Na/ Cs/La/Na/ Cs/La/Na/ Cs/La/Na/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La La/S/Sr La/S/Sr/ La/S/Sr/La/S/Sr/ La/S/Sr/ La/S/Sr/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaK/La/Zr/Ag K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Lu/Tl Lu/Tl/ Lu/Tl/ Lu/Tl/Lu/Tl/ Lu/Tl/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Pr/Zn Pr/Zn/Pr/Zn/ Pr/Zn/ Pr/Zn/ Pr/Zn/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaRb/Sr/L Rb/Sr/La/ Rb/Sr/La/ Rb/Sr/La/ Rb/Sr/La/ Rb/Sr/La/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Na/Sr/Eu/Ca Na/Sr/Eu/Ca/Na/Sr/Eu/Ca/ Na/Sr/Eu/Ca/ Na/Sr/Eu/Ca/ Na/Sr/Eu/Ca/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La K/Cs/Sr/La K/Cs/Sr/La/ K/Cs/Sr/La/ K/Cs/Sr/La/K/Cs/Sr/La/ K/Cs/Sr/La/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaNa/Sr/Lu Na/Sr/Lu/ Na/Sr/Lu/ Na/Sr/Lu/ Na/Sr/Lu/ Na/Sr/Lu/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sr/Eu/Dy Sr/Eu/Dy/ Sr/Eu/Dy/Sr/Eu/Dy/ Sr/Eu/Dy/ Sr/Eu/Dy/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaLu/Nb Lu/Nb/ Lu/Nb/ Lu/Nb/ Lu/Nb/ Lu/Nb/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La La/Dy/Gd La/Dy/Gd/ La/Dy/Gd/ La/Dy/Gd/ La/Dy/Gd/ La/Dy/Gd/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Na/Mg/Tl/P Na/Mg/Tl/P/Na/Mg/Tl/P/ Na/Mg/Tl/P/ Na/Mg/Tl/P/ Na/Mg/Tl/P/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Na/Pt Na/Pt/ Na/Pt/ Na/Pt/ Na/Pt/ Na/Pt/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Gd/Li/K Gd/Li/K/ Gd/Li/K/Gd/Li/K/ Gd/Li/K/ Gd/Li/K/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaRb/K/Lu Rb/K/Lu/ Rb/K/Lu/ Rb/K/Lu/ Rb/K/Lu/ Rb/K/Lu/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Sr/La/Dy/S Sr/La/Dy/S/ Sr/La/Dy/S/ Sr/La/Dy/S/Sr/La/Dy/S/ Sr/La/Dy/S/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaNa/Ce/Co Na/Ce/Co/ Na/Ce/Co/ Na/Ce/Co/ Na/Ce/Co/ Na/Ce/Co/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Na/Ce Na/Ce/ Na/Ce/ Na/Ce/Na/Ce/ Na/Ce La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Na/Ga/Gd/AlNa/Ga/Gd/Al/ Na/Ga/Gd/Al/ Na/Ga/Gd/Al/ Na/Ga/Gd/Al/ Na/Ga/Gd/Al/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Ba/Rh/Ta Ba/Rh/Ta/ Ba/Rh/Ta/Ba/Rh/Ta/ Ba/Rh/Ta/ Ba/Rh/Ta/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaBa/Ta Ba/Ta/ Ba/Ta/ Ba/Ta/ Ba/Ta/ Ba/Ta/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Na/Al/Bi/ Na/Al/Bi/ Na/Al/Bi/ Na/Al/Bi/ Na/Al/Bi/ Na/Al/Bi/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Cs/Eu/S Cs/Eu/S/ Cs/Eu/S/Cs/Eu/S/ Cs/Eu/S/ Cs/Eu/S/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaSm/Tm/Yb/Fe Sm/Tm/Yb/Fe/ Sm/Tm/Yb/Fe/ Sm/Tm/Yb/Fe/ Sm/Tm/Yb/Fe/Sm/Tm/Yb/Fe/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sm/Tm/YbSm/Tm/Yb/ Sm/Tm/Yb/ Sm/Tm/Yb/ Sm/Tm/Yb/ Sm/Tm/Yb/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Hf/Zr/Ta Hf/Zr/Ta/ Hf/Zr/Ta/ Hf/Zr/Ta/ Hf/Zr/Ta/Hf/Zr/Ta La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Rb/Gd/Li/KRb/Gd/Li/K/ Rb/Gd/Li/K/ Rb/Gd/Li/K/ Rb/Gd/Li/K/ Rb/Gd/Li/K/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Gd/Ho/Al/P Gd/Ho/Al/P/Gd/Ho/Al/P/ Gd/Ho/Al/P/ Gd/Ho/Al/P/ Gd/Ho/Al/P/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Na/Ca/Lu Na/Ca/Lu/ Na/Ca/Lu/ Na/Ca/Lu/ Na/Ca/Lu/Na/Ca/Lu/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Cu/Sn Cu/Sn/ Cu/Sn/Cu/Sn/ Cu/Sn/ Cu/Sn/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Ag/AuAg/Au/ Ag/Au/ Ag/Au/ Ag/Au/ Ag/Au/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-LaCe-La Al/Bi Al/Bi/ Al/Bi/ Al/Bi/ Al/Bi/ Al/Bi/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Al/Mo Al/Mo/ Al/Mo/ Al/Mo/ Al/Mo/ Al/Mo/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Al/Nb Al/Nb/ Al/Nb/ Al/Nb/Al/Nb/ Al/Nb/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Au/Pt Au/Pt/Au/Pt/ Au/Pt/ Au/Pt/ Au/Pt/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaGa/Bi Ga/Bi/ Ga/Bi/ Ga/Bi/ Ga/Bi/ Ga/Bi/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Mg/W Mg/W/ Mg/W/ Mg/W/ Mg/W/ Mg/W/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Pb/Au/ Pb/Au/ Pb/Au/ Pb/Au/ Pb/Au/ Pb/Au/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sn/Mg Sn/Mg/ Sn/Mg/ Sn/Mg/Sn/Mg/ Sn/Mg/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Zn/Bi Zn/Bi/Zn/Bi/ Zn/Bi/ Zn/Bi/ Zn/Bi/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaSr/Ta Sr/Ta/ Sr/Ta/ Sr/Ta/ Sr/Ta/ Sr/Ta/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Na Na/ Na/ Na/ Na/ Na/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-LaCe-La Sr Sr/ Sr/ Sr/ Sr/ Sr/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaCa Ca/ Ca/ Ca/ Ca/ Ca/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Yb Yb/Yb/ Yb/ Yb/ Yb/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Cs Cs/ Cs/ Cs/Cs/ Cs/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sb Sb/ Sb/ Sb/ Sb/ Sb/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Zn/Bi Zn/Bi Zn/Bi Zn/Bi Zn/BiGd/Ho Gd/Ho/ Gd/Ho/ Gd/Ho/ Gd/Ho/ Gd/Ho/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Zr/Bi Zr/Bi/ Zr/Bi/ Zr/Bi/ Zr/Bi/ Zr/Bi/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Ho/Sr Ho/Sr/ Ho/Sr/ Ho/Sr/ Ho/Sr/ Ho/Sr/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Gd/Ho/Sr Gd/Ho/Sr/ Gd/Ho/Sr/Gd/Ho/Sr/ Gd/Ho/Sr/ Gd/Ho/Sr/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-LaCa/Sr Ca/Sr/ Ca/Sr/ Ca/Sr/ Ca/Sr/ Ca/Sr/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Ca/Sr/W Ca/Sr/W/ Ca/Sr/W/ Ca/Sr/W/ Ca/Sr/W/ Ca/Sr/W/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Na/Zr/Eu/Tm Na/Zr/Eu/Tm/Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Sr/Ho/Tm/Na Sr/Ho/Tm/Na/ Sr/Ho/Tm/Na/Sr/Ho/Tm/Na/ Sr/Ho/Tm/Na/ Sr/Ho/Tm/Na/ La_(3.8)Nd_(0.2)O6 Y-La Zr-LaPr-La Ce-La Sr/Pb Sr/Pb/ Sr/Pb/ Sr/Pb/ Sr/Pb/ Sr/Pb/ La_(3.8)Nd_(0.2)O6Y-La Zr-La Pr-La Ce-La Sr/W/Li Sr/W/Li/ Sr/W/Li/ Sr/W/Li/ Sr/W/Li/Sr/W/Li/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Ca/Sr/W Ca/Sr/W/Ca/Sr/W/ Ca/Sr/VV/ Ca/Sr/W/ Ca/Sr/W/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-LaCe-La Sr/Hf Sr/Hf/ Sr/Hf/ Sr/Hf/ Sr/Hf/ Sr/Hf/ La_(3.8)Nd_(0.2)O6 Y-LaZr-La Pr-La Ce-La Au/Re Au/Re/ Au/Re/ Au/Re/ Au/Re/ Au/Re/La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La Sr/W Sr/W/ Sr/W/ Sr/W/ Sr/W/Sr/W/ La_(3.8)Nd_(0.2)O6 Y-La Zr-La Pr-La Ce-La La/Nd La/Nd/ La/Nd/La/Nd/ La/Nd/ La/Nd/ La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-La La/SmLa/Sm/ La/Sm/ La/Sm/ La/Sm/ La/Sm/ La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-LaCe-La La/Ce La/Ce/ La/Ce/ La/Ce/ La/Ce/ La/Ce/ La_(3.8)Nd_(0.2)O₆ Y-LaZr-La Pr-La Ce-La La/Sr La/Sr/ La/Sr/ La/Sr/ La/Sr/ La/Sr/La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-La La/Nd/Sr La/Nd/Sr/ La/Nd/Sr/La/Nd/Sr/ La/Nd/Sr/ La/Nd/Sr/ La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-LaLa/Bi/Sr La/Bi/Sr/ La/Bi/Sr/ La/Bi/Sr/ La/Bi/Sr/ La/Bi/Sr/La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-La La/Ce/Nd/Sr La/Ce/Nd/Sr/La/Ce/Nd/Sr/ La/Ce/Nd/Sr/ La/Ce/Nd/Sr/ La/Ce/Nd/Sr/ La_(3.8)Nd_(0.2)O₆Y-La Zr-La Pr-La Ce-La La/Bi/Ce/Nd/Sr La/Bi/Ce/Nd/Sr/ La/Bi/Ce/Nd/Sr/La/Bi/Ce/Nd/Sr/ La/Bi/Ce/Nd/S La/Bi/Ce/Nd/Sr/ La_(3.8)Nd_(0.2)O₆ Y-LaZr-La Pr-La Ce-La Eu/Gd Eu/Gd/ Eu/Gd/ Eu/Gd/ Eu/Gd/ Eu/Gd/La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-La Ca/Na Ca/Na/ Ca/Na/ Ca/Na/Ca/Na/ Ca/Na/ La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-La Eu/Sm Eu/Sm/Eu/Sm/ Eu/Sm/ Eu/Sm/ Eu/Sm/ La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-LaEu/Sr Eu/Sr/ Eu/Sr/ Eu/Sr/ Eu/Sr/ Eu/Sr/ La_(3.8)Nd_(0.2)O₆ Y-La Zr-LaPr-La Ce-La Mg/Sr Mg/Sr/ Mg/Sr/ Mg/Sr/ Mg/Sr/ Mg/Sr/ La_(3.8)Nd_(0.2)O₆Y-La Zr-La Pr-La Ce-La Ce/Mg Ce/Mg/ Ce/Mg/ Ce/Mg/ Ce/Mg/ Ce/Mg/La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-La Gd/Sm Gd/Sm/ Gd/Sm/ Gd/Sm/Gd/Sm/ Gd/Sm/ La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-La Au/Pb Au/Pb/Au/Pb/ Au/Pb/ Au/Pb/ Au/Pb/ La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-LaBi/Hf Bi/Hf/ Bi/Hf/ Bi/Hf/ Bi/Hf/ Bi/Hf/ La_(3.8)Nd_(0.2)O₆ Y-La Zr-LaPr-La Ce-La Rb/S Rb/S/ Rb/S/ Rb/S/ Rb/S/ Rb/S/ La_(3.8)Nd_(0.2)O₆ Y-LaZr-La Pr-La Ce-La Sr/Nd Sr/Nd/ Sr/Nd/ Sr/Nd/ Sr/Nd/ Sr/Nd/La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-La Eu/Y Eu/Y/ Eu/Y/ Eu/Y/ Eu/Y/Eu/Y/ La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-La Mg/Nd Mg/Nd/ Mg/Nd/Mg/Nd/ Mg/Nd/ Mg/Nd/ La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-La La/MgLa/Mg/ La/Mg/ La/Mg/ La/Mg/ La/Mg/ La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-LaCe-La Mg/Nd/Fe Mg/Nd/Fe/ Mg/Nd/Fe/ Mg/Nd/Fe/ Mg/Nd/Fe/ Mg/Nd/Fe/La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-La Rb/Sr Rb/Sr/ Rb/Sr/ Rb/Sr/Rb/Sr/ Rb/Sr/ La_(3.8)Nd_(0.2)O₆ Y-La Zr-La Pr-La Ce-La

TABLE 4 CATALYSTS (CAT) DOPED WITH SPECIFIC DOPANTS (DOP) Dop\CatLn1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Eu/Na Eu/Na/ Eu/Na/ Eu/Na/Eu/Na/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/Na Sr/Na/ Sr/Na/Sr/Na/ Sr/Na/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/Zr/Eu/CaNa/Zr/Eu/Ca/ Na/Zr/Eu/Ca/ Na/Zr/Eu/Ca/ Na/Zr/Eu/Ca/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Mg/Na Mg/Na/ Mg/Na/ Mg/Na/ Mg/Na/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/Sm/Ho/Tm Sr/Sm/Ho/Tm/Sr/Sm/Ho/Tm/ Sr/Sm/Ho/Tm/ Sr/Sm/Ho/Tm/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/W Sr/W/ Sr/W/ Sr/W/ Sr/W/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Mg/La/K Mg/La/K/ Mg/La/K/Mg/La/K/ Mg/La/K/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgONa/K/Mg/Tm Na/K/Mg/Tm/ Na/K/Mg/Tm/ Na/K/Mg/Tm/ Na/K/Mg/Tm/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/Dy/K Na/Dy/K/ Na/Dy/K/Na/Dy/K/ Na/Dy/K/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/La/DyNa/La/Dy/ Na/La/Dy/ Na/La/Dy/ Na/La/Dy/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/La/Eu Na/La/Eu/ Na/La/Eu/ Na/La/Eu/Na/La/Eu/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/La/Eu/InNa/La/Eu/In/ Na/La/Eu/In/ Na/La/Eu/In/ Na/La/Eu/In/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/La/K Na/La/K/ Na/La/K/ Na/La/K/ Na/La/K/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/La/Li/Cs Na/La/Li/Cs/Na/La/Li/Cs/ Na/La/Li/Cs/ Na/La/Li/Cs/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO K/La K/La/ K/La/ K/La/ K/La/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO K/La/S K/La/S/ K/La/S/K/La/S/ K/La/S/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO K/Na K/Na/K/Na/ K/Na/ K/Na/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Li/CsLi/Cs/ Li/Cs/ Li/Cs/ Li/Cs/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Li/Cs/La Li/Cs/La/ Li/Cs/La/ Li/Cs/La/ Li/Cs/La/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Li/Cs/La/Tm Li/Cs/La/Tm/ Li/Cs/La/Tm/Li/Cs/La/Tm/ Li/Cs/La/Tm/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgOLi/Cs/Sr/Tm Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/ Li/Cs/Sr/Tm/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Li/Sr/Cs Li/Sr/Cs/Li/Sr/Cs/ Li/Sr/Cs/ Li/Sr/Cs/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Li/Sr/Zn/K Li/Sr/Zn/K/ Li/Sr/Zn/K/ Li/Sr/Zn/K/ Li/Sr/Zn/K/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Li/Ga/Cs Li/Ga/Cs/Li/Ga/Cs/ Li/Ga/Cs/ Li/Ga/Cs/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Li/K/Sr/La Li/K/Sr/La/ Li/K/Sr/La/ Li/K/Sr/La/ Li/K/Sr/La/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Li/Na Li/Na/ Li/Na/ Li/Na/Li/Na/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Li/Na/Rb/GaLi/Na/Rb/Ga/ Li/Na/Rb/Ga/ Li/Na/Rb/Ga/ Li/Na/Rb/Ga/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Li/Na/Sr Li/Na/Sr/ Li/Na/Sr/ Li/Na/Sr/Li/Na/Sr/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Li/Na/Sr/LaLi/Na/Sr/La/ Li/Na/Sr/La/ Li/Na/Sr/La/ Li/Na/Sr/La/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Li/Sm/Cs Li/Sm/Cs/ Li/Sm/Cs/ Li/Sm/Cs/Li/Sm/Cs/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ba/Sm/Yb/SBa/Sm/Yb/S/ Ba/Sm/Yb/S/ Ba/Sm/Yb/S/ Ba/Sm/Yb/S/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ba/Tm/K/La Ba/Tm/K/La/ Ba/Tm/K/La/Ba/Tm/K/La/ Ba/Tm/K/La/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgOBa/Tm/Zn/K Ba/Tm/Zn/K/ Ba/Tm/Zn/K/ Ba/Tm/Zn/K/ Ba/Tm/Zn/K/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO C+s/K/La Cs/K/La/ Cs/K/La/Cs/K/La/ Cs/K/La/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgOCs/La/Tm/Na Cs/La/Tm/Na/ Cs/La/Tm/Na/ Cs/La/Tm/Na/ Cs/La/Tm/Na/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Cs/Li/K/La Cs/Li/K/La/Cs/Li/K/La/ Cs/Li/K/La/ Cs/Li/K/La/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆Y₂O₃ MgO Sm/Li/Sr/Cs Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/ Sm/Li/Sr/Cs/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/Cs/La Sr/Cs/La/Sr/Cs/La/ Sr/Cs/La/ Sr/Cs/La/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Sr/Tm/Li/Cs Sr/Tm/Li/Cs/ Sr/Tm/Li/Cs/ Sr/Tm/Li/Cs/ Sr/Tm/Li/Cs/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Zn/K Zn/K/ Zn/K/ Zn/K/Zn/K/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Zr/Cs/K/LaZr/Cs/K/La/ Zr/Cs/K/La/ Zr/Cs/K/La/ Zr/Cs/K/La/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Rb/Ca/In/Ni Rb/Ca/In/Ni/ Rb/Ca/In/Ni/Rb/Ca/In/Ni/ Rb/Ca/In/Ni/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgOSr/Ho/Tm Sr/Ho/Tm/ Sr/Ho/Tm/ Sr/Ho/Tm/ Sr/Ho/Tm/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO La/Nd/S La/Nd/S/ La/Nd/S/ La/Nd/S/ La/Nd/S/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Li/Rb/Ca Li/Rb/Ca/Li/Rb/Ca/ Li/Rb/Ca/ Li/Rb/Ca/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Li/K Li/K/ Li/K/ Li/K/ Li/K/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆Y₂O₃ MgO Tm/Lu/Ta/P Tm/Lu/Ta/P/ Tm/Lu/Ta/P/ Tm/Lu/Ta/P/ Tm/Lu/Ta/P/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Rb/Ca/Dy/P Rb/Ca/Dy/P/Rb/Ca/Dy/P/ Rb/Ca/Dy/P/ Rb/Ca/Dy/P/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆Y₂O₃ MgO Mg/La/Yb/Zn Mg/La/Yb/Zn/ Mg/La/Yb/Zn/ Mg/La/Yb/Zn/ Mg/La/Yb/Zn/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Rb/Sr/Lu Rb/Sr/Lu/Rb/Sr/Lu/ Rb/Sr/Lu/ Rb/Sr/Lu/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Na/Sr/Lu/Nb Na/Sr/Lu/Nb/ Na/Sr/Lu/Nb/ Na/Sr/Lu/Nb/ Na/Sr/Lu/Nb/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/Eu/Hf Na/Eu/Hf/Na/Eu/Hf/ Na/Eu/Hf/ Na/Eu/Hf/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Dy/Rb/Gd Dy/Rb/Gd/ Dy/Rb/Gd/ Dy/Rb/Gd/ Dy/Rb/Gd/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/Pt/Bi Na/Pt/Bi/ Na/Pt/Bi/ Na/Pt/Bi/Na/Pt/Bi/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Rb/Hf Rb/Hf/Rb/Hf/ Rb/Hf/ Rb/Hf/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ca/CsCa/Cs/ Ca/Cs/ Ca/Cs/ Ca/Cs/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Ca/Mg/Na Ca/Mg/Na/ Ca/Mg/Na/ Ca/Mg/Na/ Ca/Mg/Na/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Hf/Bi Hf/Bi/ Hf/Bi/ Hf/Bi/ Hf/Bi/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/Sn Sr/Sn/ Sr/Sn/ Sr/Sn/Sr/Sn/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/W Sr/W/ Sr/W/Sr/W/ Sr/W/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/Nb Sr/Nb/Sr/Nb/ Sr/Nb/ Sr/Nb/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Zr/WZr/W/ Zr/W/ Zr/W/ Zr/W/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgOY/W Y/W/ Y/W/ Y/W/ Y/W/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgONa/W Na/W/ Na/W/ Na/W/ Na/W/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Bi/W Bi/W/ Bi/W/ Bi/W/ Bi/W/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆Y₂O₃ MgO Bi/Cs Bi/Cs/ Bi/Cs/ Bi/Cs/ Bi/Cs/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Bi/Ca Bi/Ca/ Bi/Ca/ Bi/Ca/ Bi/Ca/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Bi/Sn Bi/Sn/ Bi/Sn/ Bi/Sn/Bi/Sn/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Bi/Sb Bi/Sb/ Bi/Sb/Bi/Sb/ Bi/Sb/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ge/Hf Ge/Hf/Ge/Hf/ Ge/Hf/ Ge/Hf/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Hf/SmHf/Sm/ Hf/Sm/ Hf/Sm/ Hf/Sm/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Sb/Ag Sb/Ag/ Sb/Ag/ Sb/Ag/ Sb/Ag/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sb/Bi Sb/Bi/ Sb/Bi/ Sb/Bi/ Sb/Bi/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sb/Au Sb/Au/ Sb/Au/ Sb/Au/Sb/Au/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sb/Sm Sb/Sm/ Sb/Sm/Sb/Sm/ Sb/Sm/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sb/Sr Sb/Sr/Sb/Sr/ Sb/Sr/ Sb/Sr/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sb/WSb/W/ Sb/W/ Sb/W/ Sb/W/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgOSb/Hf Sb/Hf/ Sb/Hf/ Sb/Hf/ Sb/Hf/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆Y₂O₃ MgO Sb/Yb Sb/Yb/ Sb/Yb/ Sb/Yb/ Sb/Yb/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sb/Sn Sb/Sn/ Sb/Sn/ Sb/Sn/ Sb/Sn/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Yb/Au Yb/Au/ Yb/Au/ Yb/Au/Yb/Au/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Yb/Ta Yb/Ta/ Yb/Ta/Yb/Ta/ Yb/Ta/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Yb/W Yb/W/Yb/W/ Yb/W/ Yb/W/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Yb/SrYb/Sr/ Yb/Sr/ Yb/Sr/ Yb/Sr/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Yb/Pb Yb/Pb/ Yb/Pb/ Yb/Pb/ Yb/Pb/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Yb/W Yb/W/ Yb/W/ Yb/W/ Yb/W/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Yb/Ag Yb/Ag/ Yb/Ag/ Yb/Ag/Yb/Ag/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Au/Sr Au/Sr/ Au/Sr/Au/Sr/ Au/Sr/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO W/Ge W/Ge/W/Ge/ W/Ge/ W/Ge/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ta/SrTa/Sr/ Ta/Sr/ Ta/Sr/ Ta/Sr/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Ta/Hf Ta/Hf/ Ta/Hf/ Ta/Hf/ Ta/Hf/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO W/Au W/Au/ W/Au/ W/Au/ W/Au/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ca/W Ca/W/ Ca/W/ Ca/W/Ca/W/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Au/Re Au/Re/ Au/Re/Au/Re/ Au/Re/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sm/Li Sm/Li/Sm/Li/ Sm/Li/ Sm/Li/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO La/KLa/K/ La/K/ La/K/ La/K/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgOZn/Cs Zn/Cs/ Zn/Cs/ Zn/Cs/ Zn/Cs/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆Y₂O₃ MgO Na/K/Mg Na/K/Mg/ Na/K/Mg/ Na/K/Mg/ Na/K/Mg/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Zr/Cs Zr/Cs/ Zr/Cs/ Zr/Cs/ Zr/Cs/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ca/Ce Ca/Ce/ Ca/Ce/ Ca/Ce/Ca/Ce/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/Li/Cs Na/Li/Cs/Na/Li/Cs/ Na/Li/Cs/ Na/Li/Cs/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Li/Sr Li/Sr/ Li/Sr/ Li/Sr/ Li/Sr/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO La/Dy/K La/Dy/K/ La/Dy/K/ La/Dy/K/ La/Dy/K/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Dy/K Dy/K/ Dy/K/ Dy/K/Dy/K/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO La/Mg La/Mg/ La/Mg/La/Mg/ La/Mg/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/Nd/In/KNa/Nd/In/K/ Na/Nd/In/K/ Na/Nd/In/K/ Na/Nd/In/K/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO In/Sr In/Sr/ In/Sr/ In/Sr/ In/Sr/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/Cs Sr/Cs/ Sr/Cs/ Sr/Cs/Sr/Cs/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Rb/Ga/Tm/CsRb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/ Rb/Ga/Tm/Cs/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ga/Cs Ga/Cs/ Ga/Cs/ Ga/Cs/ Ga/Cs/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO K/La/Zr/Ag K/La/Zr/Ag/K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆Y₂O₃ MgO Lu/Fe Lu/Fe/ Lu/Fe/ Lu/Fe/ Lu/Fe/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/Tm Sr/Tm/ Sr/Tm/ Sr/Tm/ Sr/Tm/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO La/Dy La/Dy/ La/Dy/ La/Dy/La/Dy/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sm/Li/Sr Sm/Li/Sr/Sm/Li/Sr/ Sm/Li/Sr/ Sm/Li/Sr/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Mg/K Mg/K/ Mg/K/ Mg/K/ Mg/K/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆Y₂O₃ MgO Li/Rb/Ga Li/Rb/Ga/ Li/Rb/Ga/ Li/Rb/Ga/ Li/Rb/Ga/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Li/Cs/Tm Li/Cs/Tm/Li/Cs/Tm/ Li/Cs/Tm/ Li/Cs/Tm/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Zr/K Zr/K/ Zr/K/ Zr/K/ Zr/K/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆Y₂O₃ MgO Li/Cs Li/Cs/ Li/Cs/ Li/Cs/ Li/Cs/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Li/K/La Li/K/La/ Li/K/La/ Li/K/La/ Li/K/La/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ce/Zr/La Ce/Zr/La/Ce/Zr/La/ Ce/Zr/La/ Ce/Zr/La/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Ca/Al/La Ca/Al/La/ Ca/Al/La/ Ca/Al/La/ Ca/Al/La/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/Zn/La Sr/Zn/La/ Sr/Zn/La/ Sr/Zn/La/Sr/Zn/La/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/Cs/ZnSr/Cs/Zn/ Sr/Cs/Zn/ Sr/Cs/Zn/ Sr/Cs/Zn/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sm/Cs Sm/Cs/ Sm/Cs/ Sm/Cs/ Sm/Cs/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO In/K In/K/ In/K/ In/K/In/K/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ho/Cs/Li/LaHo/Cs/Li/La/ Ho/Cs/Li/La/ Ho/Cs/Li/La/ Ho/Cs/Li/La/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Cs/La/Na Cs/La/Na/ Cs/La/Na/ Cs/La/Na/Cs/La/Na/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO La/S/Sr La/S/Sr/La/S/Sr/ La/S/Sr/ La/S/Sr/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgOK/La/Zr/Ag K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/ K/La/Zr/Ag/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Lu/Tl Lu/Tl/ Lu/Tl/ Lu/Tl/Lu/Tl/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Pr/Zn Pr/Zn/ Pr/Zn/Pr/Zn/ Pr/Zn/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Rb/Sr/LRb/Sr/La/ Rb/Sr/La/ Rb/Sr/La/ Rb/Sr/La/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/Sr/Eu/Ca Na/Sr/Eu/Ca/ Na/Sr/Eu/Ca/Na/Sr/Eu/Ca/ Na/Sr/Eu/Ca/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgOK/Cs/Sr/La K/Cs/Sr/La/ K/Cs/Sr/La/ K/Cs/Sr/La/ K/Cs/Sr/La/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/Sr/Lu Na/Sr/Lu/Na/Sr/Lu/ Na/Sr/Lu/ Na/Sr/Lu/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Sr/Eu/Dy Sr/Eu/Dy/ Sr/Eu/Dy/ Sr/Eu/Dy/ Sr/Eu/Dy/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Lu/Nb Lu/Nb/ Lu/Nb/ Lu/Nb/ Lu/Nb/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO La/Dy/Gd La/Dy/Gd/La/Dy/Gd/ La/Dy/Gd/ La/Dy/Gd/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Na/Mg/Tl/P Na/Mg/Tl/P/ Na/Mg/Tl/P/ Na/Mg/Tl/P/ Na/Mg/Tl/P/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/Pt Na/Pt/ Na/Pt/ Na/Pt/Na/Pt/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Gd/Li/K Gd/Li/K/Gd/Li/K/ Gd/Li/K/ Gd/Li/K/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgORb/K/Lu Rb/K/Lu/ Rb/K/Lu/ Rb/K/Lu/ Rb/K/Lu/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/La/Dy/S Sr/La/Dy/S/ Sr/La/Dy/S/Sr/La/Dy/S/ Sr/La/Dy/S/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgONa/Ce/Co Na/Ce/Co/ Na/Ce/Co/ Na/Ce/Co/ Na/Ce/Co/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/Ce Na/Ce/ Na/Ce/ Na/Ce/ Na/Ce/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/Ga/Gd/Al Na/Ga/Gd/Al/Na/Ga/Gd/Al/ Na/Ga/Gd/Al/ Na/Ga/Gd/Al/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ba/Rh/Ta Ba/Rh/Ta/ Ba/Rh/Ta/ Ba/Rh/Ta/Ba/Rh/Ta/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ba/Ta Ba/Ta/Ba/Ta/ Ba/Ta/ Ba/Ta/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgONa/Al/Bi/ Na/Al/Bi/ Na/Al/Bi/ Na/Al/Bi/ Na/Al/Bi/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Cs/Eu/S Cs/Eu/S/ Cs/Eu/S/ Cs/Eu/S/ Cs/Eu/S/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sm/Tm/Yb/Fe Sm/Tm/Yb/Fe/Sm/Tm/Yb/Fe/ Sm/Tm/Yb/Fe/ Sm/Tm/Yb/Fe/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sm/Tm/Yb Sm/Tm/Yb/ Sm/Tm/Yb/ Sm/Tm/Yb/Sm/Tm/Yb/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Hf/Zr/TaHf/Zr/Ta/ Hf/Zr/Ta/ Hf/Zr/Ta/ Hf/Zr/Ta/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Rb/Gd/Li/K Rb/Gd/Li/K/ Rb/Gd/Li/K/Rb/Gd/Li/K/ Rb/Gd/Li/K/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgOGd/Ho/Al/P Gd/Ho/Al/P/ Gd/Ho/Al/P/ Gd/Ho/Al/P/ Gd/Ho/Al/P/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na/Ca/Lu Na/Ca/Lu/Na/Ca/Lu/ Na/Ca/Lu/ Na/Ca/Lu/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Cu/Sn Cu/Sn/ Cu/Sn/ Cu/Sn/ Cu/Sn/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ag/Au Ag/Au/ Ag/Au/ Ag/Au/ Ag/Au/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Al/Bi Al/Bi/ Al/Bi/ Al/Bi/Al/Bi/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Al/Mo Al/Mo/ Al/Mo/Al/Mo/ Al/Mo/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Al/Nb Al/Nb/Al/Nb/ Al/Nb/ Al/Nb/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Au/PtAu/Pt/ Au/Pt/ Au/Pt/ Au/Pt/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Ga/Bi Ga/Bi/ Ga/Bi/ Ga/Bi/ Ga/Bi/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Mg/W Mg/W/ Mg/W/ Mg/W/ Mg/W/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Pb/Au/ Pb/Au/ Pb/Au/Pb/Au/ Pb/Au/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sn/Mg Sn/Mg/Sn/Mg/ Sn/Mg/ Sn/Mg/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Zn/BiZn/Bi/ Zn/Bi/ Zn/Bi/ Zn/Bi/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Sr/Ta Sr/Ta/ Sr/Ta/ Sr/Ta/ Sr/Ta/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Na Na/ Na/ Na/ Na/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr Sr/ Sr/ Sr/ Sr/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ca Ca/ Ca/ Ca/ Ca/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Yb Yb/ Yb/ Yb/ Yb/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Cs Cs/ Cs/ Cs/ Cs/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sb Sb/ Sb/ Sb/ Sb/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Gd/Ho Gd/Ho/ Gd/Ho/ Gd/Ho/ Gd/Ho/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Zr/Bi Zr/Bi/ Zr/Bi/ Zr/Bi/Zr/Bi/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ho/Sr Ho/Sr/ Ho/Sr/Ho/Sr/ Ho/Sr/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Gd/Ho/SrGd/Ho/Sr/ Gd/Ho/Sr/ Gd/Ho/Sr/ Gd/Ho/Sr/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ca/Sr Ca/Sr/ Ca/Sr/ Ca/Sr/ Ca/Sr/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ca/Sr/W Ca/Sr/W/ Ca/Sr/W/Ca/Sr/W/ Ca/Sr/W/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgONa/Zr/Eu/Tm Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/ Na/Zr/Eu/Tm/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/Ho/Tm/Na Sr/Ho/Tm/Na/Sr/Ho/Tm/Na/ Sr/Ho/Tm/Na/ Sr/Ho/Tm/Na/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/Pb Sr/Pb/ Sr/Pb/ Sr/Pb/ Sr/Pb/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/W/Li Sr/W/Li/ Sr/W/Li/Sr/W/Li/ Sr/W/Li/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ca/Sr/WCa/Sr/W/ Ca/Sr/W/ Ca/Sr/VV/ Ca/Sr/W/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/Hf Sr/Hf/ Sr/Hf/ Sr/Hf/ Sr/Hf/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Au/Re Au/Re/ Au/Re/ Au/Re/Au/Re/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/W Sr/W/ Sr/W/Sr/W/ Sr/W/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO La/Nd La/Nd/La/Nd/ La/Nd/ La/Nd/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO La/SmLa/Sm/ La/Sm/ La/Sm/ La/Sm/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO La/Ce La/Ce/ La/Ce/ La/Ce/ La/Ce/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO La/Sr La/Sr/ La/Sr/ La/Sr/ La/Sr/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO La/Nd/Sr La/Nd/Sr/La/Nd/Sr/ La/Nd/Sr/ La/Nd/Sr/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO La/Bi/Sr La/Bi/Sr/ La/Bi/Sr/ La/Bi/Sr/ La/Bi/Sr/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO La/Ce/Nd/Sr La/Ce/Nd/Sr/ La/Ce/Nd/Sr/La/Ce/Nd/Sr/ La/Ce/Nd/Sr/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgOLa/Bi/Ce/Nd/Sr La/Bi/Ce/Nd/Sr/ La/Bi/Ce/Nd/Sr/ La/Bi/Ce/Nd/Sr/La/Bi/Ce/Nd/S Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Eu/Gd Eu/Gd/Eu/Gd/ Eu/Gd/ Eu/Gd/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ca/NaCa/Na/ Ca/Na/ Ca/Na/ Ca/Na/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Eu/Sm Eu/Sm/ Eu/Sm/ Eu/Sm/ Eu/Sm/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Eu/Sr Eu/Sr/ Eu/Sr/ Eu/Sr/ Eu/Sr/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Mg/Sr Mg/Sr/ Mg/Sr/ Mg/Sr/Mg/Sr/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Ce/Mg Ce/Mg/ Ce/Mg/Ce/Mg/ Ce/Mg/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Gd/Sm Gd/Sm/Gd/Sm/ Gd/Sm/ Gd/Sm/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Au/PbAu/Pb/ Au/Pb/ Au/Pb/ Au/Pb/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Bi/Hf Bi/Hf/ Bi/Hf/ Bi/Hf/ Bi/Hf/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Rb/S Rb/S/ Rb/S/ Rb/S/ Rb/S/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Sr/Nd Sr/Nd/ Sr/Nd/ Sr/Nd/Sr/Nd/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Eu/Y Eu/Y/ Eu/Y/Eu/Y/ Eu/Y/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Mg/Nd Mg/Nd/Mg/Nd/ Mg/Nd/ Mg/Nd/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO La/MgLa/Mg/ La/Mg/ La/Mg/ La/Mg/ Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃MgO Mg/Nd/Fe Mg/Nd/Fe/ Mg/Nd/Fe/ Mg/Nd/Fe/ Mg/Nd/Fe/ Ln1_(4-x)Ln2_(x)O₆La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO Rb/Sr Rb/Sr/ Rb/Sr/ Rb/Sr/ Rb/Sr/Ln1_(4-x)Ln2_(x)O₆ La_(4-x)Ln1_(x)O₆ Y₂O₃ MgO

The catalysts of the disclosure may be analyzed by inductively coupledplasma mass spectrometry (ICP-MS) to determine the element content ofthe catalysts. ICP-MS is a type of mass spectrometry that is highlysensitive and capable of the determination of a range of metals andseveral non-metals at concentrations below one part in 10¹². ICP isbased on coupling together an inductively coupled plasma as a method ofproducing ions (ionization) with a mass spectrometer as a method ofseparating and detecting the ions. ICP-MS methods are well known in theart.

As used throughout the specification, a catalyst composition representedby E¹/E²/E³, etc., wherein E¹, E² and E³ are each independently anelement or a compound comprising one or more elements, refers to acatalyst comprised of a mixture of E¹, E² and E³. E¹, E² and E³, etc.are not necessarily present in equal amounts and need not form a bondwith one another. For example, a catalyst comprising Li/MgO refers to acatalyst comprising Li and MgO, for example, Li/MgO may refer to MgOdoped with Li. By way of another example, a catalyst comprisingNa/Mn/W/O refers to a catalyst comprised of a mixture of sodium,manganese, tungsten and oxygen. Generally the oxygen is in the form of ametal oxide.

In some embodiments, dopants are present in the catalysts in, forexample, less than 50 at %, less than 25 at %, less than 10 at %, lessthan 5 at % or less than 1 at %.

In other embodiments of the catalysts, the weight ratio (w/w) of thecatalyst base material to the doping element(s) ranges from 1:1 to10,000:1, 1:1 to 1,000:1 or 1:1 to 500:1.

2. Catalytic Materials

As noted above, the present disclosure includes a catalytic materialcomprising a plurality of mixed metal oxide catalysts. Typically, thecatalytic material comprises a support or carrier. The support ispreferably porous and has a high surface area. In some embodiments thesupport is active (i.e. has catalytic activity). In other embodiments,the support is inactive (i.e. non-catalytic). In some embodiments, thesupport comprises an inorganic oxide, Al₂O₃, SiO₂, TiO₂, MgO, CaO, SrO,ZrO₂, ZnO, LiAlO₂, MgAl₂O₄, MnO, MnO₂, Mn₂O₄, La₂O₃, activated carbon,silica gel, zeolites, activated clays, activated Al₂O₃, SiC,diatomaceous earth, magnesia, aluminosilicates, calcium aluminate, orcombinations thereof. In some embodiments the support comprises SiO₂. Inother embodiments the support comprises MgO. In yet other embodiments,the support comprises yttrium, for example Y₂O₃. In other embodimentsthe support comprises ZrO₂. In yet other embodiments, the supportcomprises La₂O₃.

In still other embodiments, the support comprises AlPO₄, Al₂O₃,SiO₂—Al₂O₃, CaO, SrO, TiO₂, ZrO₂, MgO, SiO₂, Z₂O₂, HfO₂, In₂O₃ orcombinations thereof. In yet other embodiments, a catalyst may serve asa support for another catalyst. For example, a catalyst may be comprisedof catalytic support material and adhered to or incorporated within thesupport is another catalyst. For example, in some embodiments, thecatalytic support may comprise SiO₂, MgO, TiO₂, ZrO₂, Al₂O₃, ZnO orcombinations thereof.

In still other embodiments, the support material comprises a carbonate.For example, in some embodiments the support material comprises MgCO₃,CaCO₃, SrCO₃, BaCO₃, Y₂(CO₃)₃, La₂(CO₃)₃ or combination thereof.

The optimum amount of catalyst present on the support depends, interalia, on the catalytic activity of the catalyst. In some embodiments,the amount of catalyst present on the support ranges from 1 to 100 partsby weight of catalyst per 100 parts by weight of support or from 10 to50 parts by weight of catalyst per 100 parts by weight of support. Inother embodiments, the amount of catalyst present on the support rangesfrom 100-200 parts of catalyst per 100 parts by weight of support, or200-500 parts of catalyst per 100 parts by weight of support, or500-1000 parts of catalyst per 100 parts by weight of support.

Typically, heterogeneous catalysts are used either in their pure form orblended with inert support materials, such as silica, alumina, etc. asdescribed above. The blending with inert materials may be used in orderto reduce and/or control large temperature non-uniformities within thereactor bed often observed in the case of strongly exothermic (orendothermic) reactions. In the case of complex multistep reactions, suchas the reaction to convert methane into ethylene (OCM), typical blendingmaterials can selectively slow down or quench one or more of the desiredreactions of the system and promote unwanted side reactions. Forexample, in the case of the oxidative coupling of methane, silica andalumina can quench the methyl radicals and thus prevent the formation ofethane. In certain aspects, the present disclosure provides a catalyticmaterial which addresses these problems typically associated withcatalyst support material. Accordingly, in certain embodiments thecatalytic activity of the catalytic material can be tuned by blendingtwo or more catalysts and/or catalyst support materials. The blendedcatalytic material may comprise a catalyst as described herein incombination with with another catalytic material, for example anadditional bulk catalyst or a catalytic nanowire as described incopending U.S. application Ser. No. 13/115,082 which is herebyincorporated by reference in its entirety, and/or inert supportmaterial.

The blended catalytic materials comprise any of the catalysts disclosedherein. For example, the blended catalytic materials may comprise aplurality of catalysts, as disclosed herein, and any one or more ofcatalytic nanowires, bulk materials and inert support materials. Thecatalytic materials may be undoped or may be doped with any of thedopants described herein.

In one embodiment, the catalyst blend comprises at least one type 1component and at least one type 2 component. Type 1 components comprisecatalysts having a high OCM activity at moderately low temperatures andtype 2 components comprise catalysts having limited or no OCM activityat these moderately low temperatures, but are OCM active at highertemperatures. For example, in some embodiments the type 1 component is acatalyst (e.g., mixed oxide of Mn/Mg, Na/Mn/W or rare earth) having highOCM activity at moderately low temperatures. For example, the type 1component may comprise a C2 yield of greater than 5% or greater than 10%at temperatures less than 800° C., less than 700° C. or less than 600°C. The type 2 component may comprise a C2 yield less than 0.1%, lessthan 1% or less than 5% at temperatures less than 800° C., less than700° C. or less than 600° C. The type 2 component may comprise a C2yield of greater than 0.1%, greater than 1%, greater than 5% or greaterthan 10% at temperatures greater than 800° C., greater than 700° C. orgreater than 600° C. Typical type 1 components include any of thecatalysts as described herein, while typical type 2 components includeother bulk OCM catalysts or catalytic nanowires. The catalyst blend mayfurther comprise inert support materials as described above (e.g.,silica, alumina, silicon carbide, etc.).

In certain embodiments, the type 2 component acts as diluent in the sameway an inert material does and thus helps reduce and/or control hotspots in the catalyst bed caused by the exothermic nature of the OCMreaction. However, because the type 2 component is an OCM catalyst,albeit not a particularly active one, it may prevent the occurrence ofundesired side reactions, e.g. methyl radical quenching. Additionally,controlling the hotspots has the beneficial effect of extending thelifetime of the catalyst.

For example, it has been found that diluting active lanthanide oxide OCMcatalysts (e.g., as described above) with as much as a 10:1 ratio ofMgO, which by itself is not an active OCM catalyst at the temperaturewhich the lanthanide oxide operates, is a good way to minimize “hotspots” in the reactor catalyst bed, while maintaining the selectivityand yield performance of the catalyst. On the other hand, doing the samedilution with quartz SiO₂ is not effective because it appears to quenchthe methyl radicals which serves to lower the selectivity to C2s.

In yet another embodiment, the type 2 components are good oxidativedehydrogenation (ODH) catalysts at the same temperature that the type 1components are good OCM catalysts. In this embodiment, theethylene/ethane ratio of the resulting gas mixture can be tuned in favorof higher ethylene. In another embodiment, the type 2 components are notonly good ODH catalysts at the same temperature the type 1 componentsare good OCM catalysts, but also have limited to moderate OCM activityat these temperatures.

In related embodiments, the catalytic performance of the catalyticmaterial is tuned by selecting specific type 1 and type 2 components ofa catalyst blend. In another embodiment, the catalytic performance istuned by adjusting the ratio of the type 1 and type 2 components in thecatalytic material. For example, the type 1 catalyst may be a catalystfor a specific step in the catalytic reaction, while the type 2 catalystmay be specific for a different step in the catalytic reaction. Forexample, the type 1 catalyst may be optimized for formation of methylradicals and the type 2 catalyst may be optimized for formation ofethane or ethylene.

In other embodiments, the catalyst material comprises at least twodifferent components (component 1, component 2, component 3, etc.). Thedifferent components may comprise different morphologies, e.g.nanowires, nanoparticles, bulk, etc. The different components in thecatalyst material can be, but not necessarily, of the same chemicalcomposition and the only difference is in the morphology and/or the sizeof the particles. This difference in morphology and particle size mayresult in a difference in reactivity at a specific temperature.Additionally, the difference in morphology and particle size of thecatalytic material components is advantageous for creating a homogeneousblend, which can have a beneficial effect on catalyst performance. Also,the difference in morphology and particle size of the blend componentswould allow for control and tuning of the macro-pore distribution in thereactor bed and thus its catalytic efficiency. An additional level ofmicro-pore tuning can be attained by blending catalysts with differentchemical composition and different morphology and/or particle size. Theproximity effect would be advantageous for the reaction selectivity.

For ease of illustration, the above description of catalytic materialsoften refers to OCM; however, such catalytic materials find utility inother catalytic reactions including but not limited to: oxidativedehydrogenation (ODH) of alkanes to their corresponding alkenes,selective oxidation of alkanes and alkenes and alkynes, oxidation of CO,dry reforming of methane, selective oxidation of aromatics,Fischer-Tropsch, combustion of hydrocarbons, etc.

OCM catalysts may be prone to hotspots due to the very exothermic natureof the OCM reaction. Diluting such catalysts helps to manage thehotspots. However, the diluent needs to be carefully chosen so that theoverall performance of the catalyst is not degraded. Silicon carbide forexample can be used as a diluent with little impact on the OCMselectivity of the blended catalytic material whereas using silica as adiluent may significantly reduce OCM selectivity. The good heatconductivity of SiC is also beneficial in minimizing hot spots.

Use of a catalyst diluent or support material that is itself OCM activehas significant advantages over more traditional diluents such as silicaand alumina, which can quench methyl radicals and thus reduce the OCMperformance of the catalyst. An OCM active diluent is not expected tohave any adverse impact on the generation and lifetime of methylradicals and thus the dilution should not have any adverse impact on thecatalyst performance. Thus embodiments of the invention include catalystcompositions comprising an OCM catalyst (e.g., any of the disclosedcatalysts) in combination with a diluent or support material that isalso OCM active. Methods for use of the same in an OCM reaction are alsoprovided.

In some embodiments, the above diluent comprises alkaline earth metalcompounds, for example alkaline metal oxides, carbonates, sulfates orphosphates. Examples of diluents useful in various embodiments include,but are not limited to, MgO, MgCO₃, MgSO₄, Mg₃(PO₄)₂, MgAl₂O₄, CaO,CaCO₃, CaSO₄, Ca₃(PO₄)₂, CaAl₂O₄, SrO, SrCO₃, SrSO₄, Sr₃(PO₄)₂, SrAl₂O₄,BaO, BaCO₃, BaSO₄, Ba₃(PO₄)₂, BaAl₂O₄ and the like. Most of thesecompounds are very cheap, especially MgO, CaO, MgCO₃, CaCO₃, SrO, SrCO₃and thus very attractive for use as diluents from an economic point ofview. Additionally, the magnesium, calcium and strontium compounds arealso environmentally friendly. Accordingly, an embodiment of theinvention provides a catalytic material comprising a catalyst incombination with a diluent selected from one or more of MgO, MgCO₃,MgSO₄, Mg₃(PO₄)₂, CaO, CaCO₃, CaSO₄, Ca₃(PO₄)₂, SrO, SrCO₃, SrSO₄,Sr₃(PO₄)₂, BaO, BaCO₃, BaSO₄, Ba₃(PO₄)₂. In some specific embodimentsthe diluents is MgO, CaO, SrO, MgCO₃, CaCO₃, SrCO₃ or combinationthereof. Methods for use of the foregoing catalytic materials in an OCMreaction are also provided. The methods comprise converting methane toethane and/or ethylene in the presence of the catalytic materials.

The above diluents and supports may be employed in any number ofmethods. For example, in some embodiments a support (e.g., MgO, CaO,CaCO₃, SrCO₃) may be used in the form of a pellet or monolith (e.g.,honeycomb) structure, and the catalysts may be impregnated or supportedthereon. In other embodiments, a core/shell arrangement is provided andthe the support material may form part of the core or shell. Forexample, a core of MgO, CaO, CaCO₃ or SrCO₃ may be coated with a shellof any of the disclosed catalyst compositions.

In some embodiments, the diluent has a morphology selected from bulk(e.g. commercial grade), nano (nanowires, for example as described incopending U.S. application Ser. No. 13/115,082, which is herebyincorporated by reference in its entirety, nanorods, nanoparticles,etc.) or combinations thereof.

In some embodiments, the diluent has zero to moderate catalytic activityat the temperature the OCM catalyst is operated. In some otherembodiments, the diluent has moderate to large catalytic activity at atemperature higher than the temperature the OCM catalyst is operated. Inyet some other embodiments, the diluent has zero to moderate catalyticactivity at the temperature the OCM catalyst is operated and moderate tolarge catalytic activity at temperatures higher than the temperature theOCM catalyst is operated. Typical temperatures for operating an OCMreaction according to the present disclosure are 800° C. or lower, 750°C. or lower, 700° C. or lower, 650° C. or lower, 600° C. or lower and550° C. or lower.

For example, CaCO₃ is a relatively good OCM catalyst at T>750° C. (50%selectivity, >20% conversion) but has essentially no activity below 700°C. Accordingly, dilution of OCM catalysts with a CaCO₃ (or SrO₃)material is expected to result in no degradation of OCM performance and,in some cases, even better performance than the neat catalyst.

In some embodiments, the diluent portion in the catalyst/diluent mixtureis 0.01%, 10%, 30%, 50%, 70%, 90% or 99.99% (weight percent) or anyother value between 0.01% and 99.9%. In some embodiments, the dilutionis performed with the OCM catalyst ready to go, e.g. after calcination.In some other embodiments, the dilution is performed prior to the finalcalcination of the catalyst, i.e. the catalyst and the diluent arecalcined together. In yet some other embodiments, the dilution can bedone during the synthesis as well, so that, for example, a mixed oxideis formed.

In some embodiments, the catalyst/diluent mixture comprises more thanone catalyst and/or more than one diluent. In some other embodiments,the catalyst/diluent mixture is pelletized and sized, or made intoshaped extrudates or deposited on a monolith or foam, or is used as itis. Methods of the invention include taking advantage of the veryexothermic nature of OCM by diluting the catalyst with another catalystthat is (almost) inactive in the OCM reaction at the operatingtemperature of the first catalyst but active at higher temperature. Inthese methods, the heat generated by the hotspots of the first catalystwill provide the necessary heat for the second catalyst to becomeactive.

3. Preparation of Catalysts and Catalytic Materials

The catalytic materials can be prepared according to any number ofmethods known in the art. For example, the catalytic materials can beprepared after preparation of the individual components by mixing theindividual components in their dry form, e.g. blend of powders, andoptionally, ball milling can be used to reduce particle size and/orincrease mixing. Each component can be added together or one after theother to form layered particles. Alternatively, the individualcomponents can be mixed prior to calcination, after calcination or bymixing already calcined components with uncalcined components. Thecatalytic materials may also be prepared by mixing the individualcomponents in their dry form and optionally pressing them together intoa “pill” followed by calcination to above 800° C., or above 900° C.

The foregoing catalysts may be doped prior to, or after formation of themixed oxide. In one embodiment, one or more metal salts are mixed toform a solution or a slurry which is dried and then calcined in a rangeof 400° C. to 900° C., or between 500° C. and 700° C. In anotherembodiment, the mixed oxide is formed first through calcination of ametal salt followed by contact with a solution comprising the dopingelement followed by drying and/or calcination between 300° C. and 800°C., or between 400° C. and 700° C.

In other examples, the catalytic materials are prepared by mixing theindividual components with one or more solvents into a suspension orslurry, and optional mixing and/or ball milling can be used to maximizeuniformity and reduce particle size. Examples of slurry solvents usefulin this context include, but are not limited to: water, alcohols,ethers, carboxylic acids, ketones, esters, amides, aldehydes, amines,alkanes, alkenes, alkynes, aromatics, etc. In other embodiments, the theindividual components are deposited on a supporting material such assilica, alumina, magnesia, activated carbon, and the like, or by mixingthe individual components using a fluidized bed granulator. Combinationsof any of the above methods may also be used.

The catalytic materials may optionally comprise a dopant as described inmore detail herein. In this respect, doping material(s) may be addedduring preparation of the individual components, after preparation ofthe individual components but before drying of the same, after thedrying step but before calcinations or after calcination. If more thanone doping material is used, each dopant can be added together or oneafter the other to form layers of dopants.

Doping material(s) may also be added as dry components and optionallyball milling can be used to increase mixing. In other embodiments,doping material(s) are added as a liquid (e.g. solution, suspension,slurry, etc.) to the dry individual catalyst components or to theblended catalytic material. The amount of liquid may optionally beadjusted for optimum wetting of the catalyst, which can result inoptimum coverage of catalyst particles by doping material. Mixing and/orball milling can also be used to maximize doping coverage and uniformdistribution. Alternatively, doping material(s) are added as a liquid(e.g. solution, suspension, slurry, etc.) to a suspension or slurry ofthe catalyst in a solvent. Incorporation of dopants can also be achievedusing any of the methods described elsewhere herein.

As noted herein, an optional calcination step usually follows anoptional drying step at T<200° C. (typically 60-120° C.) in a regularoven or in a vacuum oven. Calcination may be performed on the individualcomponents of the catalytic material or on the blended catalyticmaterial. Calcination is generally performed in an oven/furnace at atemperature higher than the minimum temperature at which at least one ofthe components decomposes or undergoes a phase transformation and can beperformed in inert atmosphere (e.g. N₂, Ar, He, etc.), oxidizingatmosphere (air, O₂, etc.) or reducing atmosphere (H₂, H₂/N₂, H₂/Ar,etc.). The atmosphere may be a static atmosphere or a gas flow and maybe performed at ambient pressure, at p<1 atm, in vacuum or at p>1 atm.High pressure treatment (at any temperature) may also be used to inducephase transformation including amorphous to crystalline.

Calcination is generally performed in any combination of stepscomprising ramp up, dwell and ramp down. For example, ramp to 500° C.,dwell at 500° C. for 5 h, ramp down to RT. Another example includes rampto 100° C., dwell at 100° C. for 2 h, ramp to 300° C., dwell at 300° C.for 4 h, ramp to 550° C., dwell at 550° C. for 4 h, ramp down to RT.Calcination conditions (pressure, atmosphere type, etc.) can be changedduring the calcination. In some embodiments, calcination is performedbefore preparation of the blended catalytic material (i.e., individualcomponents are calcined), after preparation of the blended catalyticmaterial but before doping, after doping of the individual components orblended catalytic material. Calcination may also be performed multipletimes, e.g. after catalyst preparation and after doping and may also beperformed by microwave heating.

The catalytic materials may be incorporated into a reactor bed forperforming any number of catalytic reactions (e.g., OCM, ODH and thelike). Accordingly, in one embodiment the present disclosure provides acatalytic material as disclosed herein in contact with a reactor and/orin a reactor bed. For example, the reactor may be for performing an OCMreaction, may be a fixed bed reactor and may have a diameter greaterthan 1 inch. In this regard, the catalytic material may be packed neat(without diluents) or diluted with an inert material (e.g., sand,silica, alumina, etc.) The catalyst components may be packed uniformlyforming a homogeneous reactor bed.

The particle size of the individual components within a catalyticmaterial may also alter the catalytic activity, and other properties, ofthe same. Accordingly, in one embodiment, the catalyst is milled to atarget average particle size or the catalyst powder is sieved to selecta particular particle size. In some aspects, the catalyst powder may bepressed into pellets and the catalyst pellets can be optionally milledand or sieved to obtain the desired particle size distribution.

In some embodiments, the catalyst materials, alone or with bindersand/or diluents, can be configured into larger aggregate forms, such aspellets, extrudates, or other aggregations of catalyst particles. Forease of duscussion, such larger forms are generally referred to hereinas “pellets”. Such pellets may optionally include a binder and/orsupport material.

Catalytic materials also include any of the disclosed catalysts disposedon or adhered to a solid support. For example, the catalysts may beadhered to the surface of a monolith support. Monoliths includehoneycomb-type structures, foams and other catalytic support structuresderivable by one skilled in the art. In one embodiment, the support is ahoneycomb matrix formed from silicon carbide, and the support furthercomprises the disclosed catalysts disposed on the surface.

As the OCM reaction is very exothermic, it can be desirable to reducethe rate of conversion per unit volume of reactor in order to avoid runaway temperature rise in the catalyst bed that can result in hot spotsaffecting performance and catalyst life. One way to reduce the OCMreaction rate per unit volume of reactor is to spread the activecatalyst onto an inert support with interconnected large pores as inceramic or metallic foams (including metal alloys having reducedreactivity with hydrocarbons under OCM reaction conditions) or havingarrays of channel as in honeycomb structured ceramic or metal assembly.

In one embodiment, a catalytic material comprising a catalyst asdisclosed herein supported on a structured support is provided. Examplesof such structure supports include, but are not limited to, metal foams,Silicon Carbide or Alumina foams, corrugated metal foil arranged to formchannel arrays, extruded ceramic honeycomb, for example Cordierite(available from Corning or NGK ceramics, USA), Silicon Carbide orAlumina.

Active catalyst loading on the structured support ranges from 1 to 500mg per ml of support component, for example from 5 to 100 mg per ml ofstructure support. Cell densities on honeycomb structured supportmaterials may range from 100 to 900 CPSI (cell per square inch), forexample 200 to 600 CPSI. Foam densities may range from 10 to 100 PPI(pore per inch), for example 20 to 60 PPI.

In other embodiments, the exotherm of the OCM reaction may be at leastpartially controlled by blending the active catalytic material withcatalytically inert material, and pressing or extruding the mixture intoshaped pellets or extrudates. In some embodiments, these mixed particlesmay then be loaded into a pack-bed reactor. The Extrudates or pelletscomprise between 30% to 70% pore volume with 5% to 50% active catalystweight fraction. Useful inert materials in this regard include, but arenot limited to MgO, CaO, Al₂O₃, SiC and cordierite.

In addition to reducing the potential for hot spots within the catalyticreactor, another advantage of using a structured ceramic with large porevolume as a catalytic support is reduced flow resistance at the same gashourly space velocity versus a pack-bed containing the same amount ofcatalyst.

Yet another advantage of using such supports is that the structuredsupport can be used to provide features difficult to obtain in apack-bed reactor. For example the support structure can improve mixingor enabling patterning of the active catalyst depositions through thereactor volume. Such patterning can consist of depositing multiplelayers of catalytic materials on the support in addition to the OCMactive component in order to affect transport to the catalyst orcombining catalytic functions such as adding O2-ODH activity, CO2-OCMactivity or CO2-ODH activity to the system in addition to O2-OCM activematerial. Another patterning strategy can be to create bypass within thestructure catalyst essentially free of active catalyst to limit theoverall conversion within a given supported catalyst volume.

Yet another advantage is reduced heat capacity of the bed of thestructured catalyst over a pack bed a similar active catalyst loadingtherefore reducing startup time.

Alternatively, such catalyst on support or in pellet form approaches canbe used for other reactions besides OCM, such as ODH, dry methanereforming, FT, and all other catalytic reactions.

In yet another embodiment, the catalysts are packed in bands forming alayered reactor bed. Each layer is composed of either a catalyst of aparticular type, morphology or size or a particular blend of catalysts.In one embodiment, the catalysts blend may have better sinteringproperties, i.e. lower tendency to sinter, then a material in its pureform. Better sintering resistance is expected to increase the catalyst'slifetime and improve the mechanical properties of the reactor bed.

One skilled in the art will recognize that various combinations oralternatives of the above methods are possible, and such variations arealso included within the scope of the present disclosure.

4. Structure/Physical Characteristics of the Disclosed Catalysts

Typically, a catalytic material described herein comprises a pluralityof metal oxide particles. In certain embodiments, the catalytic materialmay further comprise a support material. The total surface area per gramof a catalytic material may have an effect on the catalytic performance.Pore size distribution may affect the catalytic performance as well.Surface area and pore size distribution of the catalytic material can bedetermined by BET (Brunauer, Emmett, Teller) measurements. BETtechniques utilize nitrogen adsorption at various temperatures andpartial pressures to determine the surface area and pore sizes ofcatalysts. BET techniques for determining surface area and pore sizedistribution are well known in the art.

In some embodiments the catalytic material comprises a surface area ofbetween 0.1 and 100 m²/g, between 1 and 100 m²/g, between 1 and 50 m²/g,between 1 and 20 m²/g, between 1 and 10 m²/g, between 1 and 5 m²/g,between 1 and 4 m²/g, between 1 and 3 m²/g, or between 1 and 2 m²/g.

Catalytic Reactions

The present disclosure provides heterogenous catalysts having bettercatalytic properties than a corresponding undoped catalyst. Thecatalysts disclosed herein are useful in any number of reactionscatalyzed by a heterogeneous catalyst. Examples of reactions wherein thedisclosed catalysts may be employed are disclosed in Farrauto andBartholomew, “Fundamentals of Industrial Catalytic Processes” BlackieAcademic and Professional, first edition, 1997, which is herebyincorporated in its entirety. Other non-limiting examples of reactionswherein the catalysts may be employed include: the oxidative coupling ofmethane (OCM) to ethane and ethylene; oxidative dehydrogenation (ODH) ofalkanes to the corresponding alkenes, for example oxidativedehydrogenation of ethane or propane to ethylene or propylene,respectively; selective oxidation of alkanes, alkenes, and alkynes;oxidation of CO, dry reforming of methane, selective oxidation ofaromatics; Fischer-Tropsch, hydrocarbon cracking; and the like.Reactions catalyzed by the disclosed catalysts are discussed in moredetail below. While an embodiment of the invention is described ingreater detail below in the context of the OCM reaction and otherreactions described herein, the catalysts are not in any way limited tothe particularly described reactions.

The disclosed catalysts are generally useful in methods for converting afirst carbon-containing compound (e.g., a hydrocarbon, CO or CO₂) to asecond carbon-containing compound. In some embodiments the methodscomprise contacting a disclosed catalyst, or material comprising thesame, with a gas comprising a first carbon-containing compound and anoxidant to produce a second carbon-containing compound. In someembodiments, the first carbon-containing compound is a hydrocarbon, CO,CO₂, methane, ethane, propane, hexane, cyclohexane, octane orcombinations thereof. In other embodiments, the second carbon-containingcompound is a hydrocarbon, CO, CO₂, ethane, ethylene, propane,propylene, hexane, hexene, cyclohexane, cyclohexene, bicyclohexane,octane, octene or hexadecane. In some embodiments, the oxidant isoxygen, ozone, nitrous oxide, nitric oxide, water, carbon dioxide orcombinations thereof.

In other embodiments of the foregoing, the method for conversion of afirst carbon-containing compound to a second carbon-containing compoundis performed at a temperature below 100° C., below 200° C., below 300°C., below 400° C., below 500° C., below 600° C., below 700° C., below800° C., below 900° C. or below 1000° C. In certain embodiments, the themethod is OCM and the method is performed at a temperature below 600°C., below 700° C., below 800° C., or below 900° C. In other embodiments,the method for conversion of a first carbon-containing compound to asecond carbon-containing compound is performed at a pressure above 0.5ATM, above 1 ATM, above 2 ATM, above 5 ATM, above 10 ATM, above 25 ATMor above 50 ATM.

The catalytic reactions described herein can be performed using standardlaboratory equipment known to those of skill in the art, for example asdescribed in U.S. Pat. No. 6,350,716, which is incorporated herein inits entirety.

As noted above, the catalysts disclosed herein have better catalyticactivity than a corresponding undoped catalyst. In some embodiments, theselectivity, yield, conversion, or combinations thereof, of a reactioncatalyzed by the catalysts is better than the selectivity, yield,conversion, or combinations thereof, of the same reaction catalyzed by acorresponding undoped catalyst under the same conditions. For example,in some embodiments, the catalyst possesses a catalytic activity suchthat yield of product in a reaction catalyzed by the catalyst is greaterthan 1.1 times, greater than 1.25 times, greater than 1.5 times, greaterthan 2.0 times, greater than 3.0 times or greater than 4.0 times theyield of product in the same reaction catalyzed by a correspondingundoped catalyst (i.e., a catalyst comprising the same base material butdifferent or no dopants).

In other embodiments, the catalyst possesses a catalytic activity suchthat selectivity for the desired product(s) in a reaction catalyzed bythe catalyst is greater than 1.1 times, greater than 1.25 times, greaterthan 1.5 times, greater than 2.0 times, greater than 3.0 times orgreater than 4.0 times the yield of product in the same reactioncatalyzed by a corresponding undoped catalyst.

In yet other embodiments, the catalyst possesses a catalytic activitysuch that conversion of reactant in a reaction catalyzed by the catalystis greater than 1.1 times, greater than 1.25 times, greater than 1.5times, greater than 2.0 times, greater than 3.0 times or greater than4.0 times the yield of product in the same reaction catalyzed by acorresponding undoped catalyst.

In yet other embodiments, the catalysts possesses a catalytic activitysuch that the activation temperature of a reaction catalyzed by thecatalyst is at least 25° C. lower, at least 50° C. lower, at least 75°C. lower, or at least 100° C. lower than the temperature of the samereaction under the same conditions but catalyzed by a correspondingundoped bulk catalyst.

Production of unwanted oxides of carbon (e.g., CO and CO₂) is a problemthat reduces overall yield of desired product and results in anenvironmental liability. Accordingly, in one embodiment the presentdisclosure addresses this problem and provides catalysts with acatalytic activity such that the selectivity for CO and/or CO₂ in areaction catalyzed by the catalysts is less than the selectivity for COand/or CO₂ in the same reaction under the same conditions but catalyzedby an undoped catalyst. Accordingly, in one embodiment, the presentdisclosure provides a catalyst which possesses a catalytic activity suchthat selectivity for CO_(x), wherein x is 1 or 2, in a reactioncatalyzed by the catalyst is less than at least 0.9 times, less than atleast 0.8 times, less than at least 0.5 times, less than at least 0.2times or less than at least 0.1 times the selectivity for CO_(x) in thesame reaction under the same conditions but catalyzed by a correspondingundoped catalyst (i.e., a catalyst comprising the same base material budifferent or no dopants).

In some embodiments, the absolute selectivity, yield, conversion, orcombinations thereof, of a reaction catalyzed by the catalysts disclosedherein is better than the absolute selectivity, yield, conversion, orcombinations thereof, of the same reaction under the same conditions butcatalyzed by a corresponding undoped catalyst. For example, in someembodiments the yield of desired product(s) in a reaction catalyzed bythe catalysts is greater than 10%, greater than 20%, greater than 30%,greater than 50%, greater than 75%, or greater than 90%. In someembodiments, the reaction is OCM and the yield of product is greaterthan 10%, greater than 20%, greater than 30% or greater than 40%. Inother embodiments, the selectivity for product in a reaction catalyzedby the catalysts is greater than 10%, greater than 20%, greater than30%, greater than 50%, greater than 75%, or greater than 90%. In otherembodiments, the conversion of reactant to product in a reactioncatalyzed by the catalysts is greater than 10%, greater than 20%,greater than 30%, greater than 50%, greater than 75%, or greater than90%.

1. Oxidative Coupling of Methane (OCM)

As noted above, the present disclosure provides catalysts havingcatalytic activity and related approaches to catalyst design andpreparation for improving the yield, selectivity and/or conversion ofany number of catalyzed reactions, including the OCM reaction. Asmentioned above, there exists a tremendous need for catalyst technologycapable of addressing the conversion of methane into high valuechemicals (e.g., ethylene and products prepared therefrom) using adirect route that does not go though syngas. Accomplishing this taskwill dramatically impact and redefine a non-petroleum based pathway forfeedstock manufacturing and liquid fuel production yielding reductionsin GHG emissions, as well as providing new fuel sources.

Ethylene has the largest carbon footprint compared to all industrialchemical products in part due to the large total volume consumed into awide range of downstream important industrial products includingplastics, surfactants and pharmaceuticals. In 2008, worldwide ethyleneproduction exceeded 120 M metric tons while growing at a robust rate of4% per year. The United States represents the largest single producer at28% of the world capacity. Ethylene is primarily manufactured from hightemperature cracking of naphtha (e.g., oil) or ethane that is separatedfrom natural gas. The true measurement of the carbon footprint can bedifficult as it depends on factors such as the feedstock and theallocation as several products are made and separated during the sameprocess. However, some general estimates can be made based on publisheddata.

Cracking consumes a significant portion (about 65%) of the total energyused in ethylene production and the remainder is for separations usinglow temperature distillation and compression. The total tons of CO₂emission per ton of ethylene are estimated at between 0.9 to 1.2 fromethane cracking and 1 to 2 from naphtha cracking. Roughly, 60% ofethylene produced is from naphtha, 35% from ethane and 5% from otherssources (Ren, T.; Patel, M. Res. Conserv. Recycl. 53:513, 2009).Therefore, based on median averages, an estimated amount of CO₂emissions from the cracking process is 114M tons per year (based on 120Mtons produced). Separations would then account for an additional 61 Mtons CO₂ per year.

The catalysts of this disclosure provide an alternative to the need forthe energy intensive cracking step. Additionally, because of the highselectivity of the catalysts, downstream separations are dramaticallysimplified, as compared to cracking which yields a wide range ofhydrocarbon products. The reaction is also exothermic so it can proceedvia an autothermal process mechanism. Overall, it is estimated that upto a potential 75% reduction in CO₂ emission compared to conventionalmethods could be achieved. This would equate to a reduction of onebillion tons of CO₂ over a ten-year period and would save over 1Mbarrels of oil per day.

The catalysts of this disclosure also permit converting ethylene intoliquid fuels such as gasoline or diesel, given ethylene's highreactivity and numerous publications demonstrating high yield reactions,in the lab setting, from ethylene to gasoline and diesel. On a lifecycle basis from well to wheel, recent analysis of methane to liquid(MTL) using F-T process derived gasoline and diesel fuels has shown anemission profile approximately 20% greater to that of petroleum basedproduction (based on a worst case scenario) (Jaramillo, P., Griffin, M.,Matthews, S., Env. Sci. Tech 42:7559, 2008). In the model, the CO₂contribution from plant energy was a dominating factor at 60%. Thus,replacement of the cracking and F-T process would be expected to providea notable reduction in net emissions, and could be produced at lower CO₂emissions than petroleum based production.

Furthermore, a considerable portion of natural gas is found in regionsthat are remote from markets or pipelines. Most of this gas is flared,re-circulated back into oil reservoirs, or vented given its low economicvalue. The World Bank estimates flaring adds 400M metric tons of CO₂ tothe atmosphere each year as well as contributing to methane emissions.The catalysts of this disclosure also provide economic and environmentalincentive to stop flaring. Also, the conversion of methane to fuel hasseveral environmental advantages over petroleum-derived fuel. Naturalgas is the cleanest of all fossil fuels, and it does not contain anumber of impurities such as mercury and other heavy metals found inoil. Additionally, contaminants including sulfur are also easilyseparated from the initial natural gas stream. The resulting fuels burnmuch cleaner with no measurable toxic pollutants and provide loweremissions than conventional diesel and gasoline in use today.

The selective, catalytic oxidative coupling of methane to ethylene (i.e.the OCM reaction) is shown by the following reaction (1):2CH₄+O₂→CH₂CH₂+2H₂O  (1)

This reaction is exothermic (Heat of Reaction −67 kcals/mole) andusually occurs at very high temperatures (>700° C.). During thisreaction, it is believed that the methane (CH₄) is first oxidativelycoupled into ethane (C₂H₆), and subsequently the ethane (C₂H₆) isoxidatively dehydrogenated into ethylene (C₂H₄). Because of the hightemperatures used in the reaction, it has been suggested that the ethaneis produced mainly by the coupling in the gas phase of thesurface-generated methyl (CH₃) radicals. Reactive metal oxides (oxygentype ions) are apparently required for the activation of CH₄ to producethe CH₃ radicals. The yield of C₂H₄ and C₂H₆ is limited by furtherreactions in the gas phase and to some extent on the catalyst surface. Afew of the possible reactions that occur during the oxidation of methaneare shown below as reactions (2) through (8):CH₄→CH₃ radical  (2)CH₃ radical→C₂H₆  (3)CH₃ radical+2.5O₂→CO₂+1.5H₂O  (4)C₂H₆→C₂H₄+H₂  (5)C₂H₆+0.5O₂→C₂H₄+H₂O  (6)C₂H₄+3O₂→2CO₂+2H₂O  (7)CH₃ radical+C_(x)H_(y)+O₂→Higher HC's−Oxidation/CO₂+H₂O  (8)

With conventional heterogeneous catalysts and reactor systems, thereported performance is generally limited to <25% CH₄ conversion at <80%combined C₂ selectivity at high temperatures (˜850° C. or higher), withthe performance characteristics of high selectivity at low conversion,or the low selectivity at high conversion. In contrast, the catalysts ofthis disclosure are highly active and can optionally operate at a lowertemperature. In one embodiment, the catalysts disclosed herein enableefficient conversion of methane to ethylene in the OCM reaction attemperatures less than when other known catalysts are used. For example,in one embodiment, the catalysts disclosed herein enable efficientconversion (i.e., high yield, conversion, and/or selectivity) of methaneto ethylene at temperatures of less than 800° C., less than 700° C. orless than 600° C. In other embodiments, the use of staged oxygenaddition, designed heat management, rapid quench and/or advancedseparations may also be employed.

Typically, the OCM reaction is run in a mixture of oxygen and nitrogenor other inert gas. Such gasses are expensive and increase the overallproduction costs associated with preparation of ethylene or ethane frommethane. However, the present inventors have now discovered that suchexpensive gases are not required and high yield, conversion,selectivity, etc. can be obtained when air is used as the gas mixtureinstead of pre-packaged and purified sources of oxygen and other gases.Accordingly, in one embodiment the disclosure provides a method forperforming the OCM reaction using air as the oxidizer source.

Accordingly, in one embodiment a stable, very active, high surface area,multifunctional catalyst is disclosed having active sites that areisolated and precisely engineered with the catalytically active metalcenters/sites in the desired proximity (see, e.g., FIG. 1) forfacilitating the OCM reaction, as well as other reactions.

The exothermic heats of reaction (free energy) follows the order ofreactions depicted above and, because of the proximity of the activesites, will mechanistically favor ethylene formation while minimizingcomplete oxidation reactions that form CO and CO₂. Representativecatalyst compositions useful for the OCM reaction include, but are notlimited to the catalyst compositions described herein.

As noted above, the presently disclosed catalysts comprise a catalyticperformance better than corresponding undoped catalysts, for example inone embodiment the catalytic performance of the catalysts in the OCMreaction is better than the catalytic performance of a correspondingundoped catalyst. In this regard, various performance criteria maydefine the “catalytic performance” of the catalysts in the OCM (andother reactions). In one embodiment, catalytic performance is defined byC2 selectivity in the OCM reaction, and the C2 selectivity of thecatalysts in the OCM reactionis >5%, >10%, >15%, >20%, >25%, >30%, >35%, >40%, >45%, >50%, >55%, >60%, >65%, >70%, >75%or >80%.

Other important performance parameters used to measure the catalysts'catalytic performance in the OCM reaction are selected from single passmethane conversion percentage (i.e., the percent of methane converted ona single pass over the catalyst or catalytic bed, etc.), reaction inletgas temperature, reaction operating temperature, total reactionpressure, methane partial pressure, gas-hour space velocity (GHSV), O₂source, catalyst stability and ethylene to ethane ratio. In certainembodiments, improved catalytic performance is defined in terms of thecatalysts' improved performance (relative to a corresponding undopedcatalyst) with respect to at least one of the foregoing performanceparameters.

The reaction inlet gas temperature in an OCM reaction catalyzed by thedisclosed catalysts can generally be maintained at a lower temperature,while maintaining better performance characteristics (e.g., conversion,C2 yield, C2 selectivity and the like) compared to the same reactioncatalyzed by a corresponding undoped catalyst under the same reactionconditions. In certain embodiments, the inlet gas temperature in an OCMreaction catalyzed by the disclosed catalysts is <700° C., <675° C.,<650° C., <625° C., <600° C., <593° C., <580° C., <570° C., <560° C.,<550° C., <540° C., <530° C., <520° C., <510° C., <500° C., <490° C.,<480° C. or even <470° C.

The reaction operating temperature in an OCM reaction catalyzed by thedisclosed catalysts can generally be maintained at a lower temperature,while maintaining better performance characteristics compared to thesame reaction catalyzed by a corresponding bulk catalyst under the samereaction conditions. In certain embodiments, the reaction operatingtemperature in an OCM reaction catalyzed by the disclosed catalysts is<700° C., <675° C., <650° C., <625° C., <600° C., <593° C., <580° C.,<570° C., <560° C., <550° C., <540° C., <530° C., <520° C., <510° C.,<500° C., <490° C., <480° C., <470° C.

The single pass methane conversion in an OCM reaction catalyzed by thecatalysts is also generally better compared to the single pass methaneconversion in the same reaction catalyzed by a corresponding undopedcatalyst under the same reaction conditions. For single pass methaneconversion it ispreferably >5%, >10%, >15%, >20%, >25%, >30%, >35%, >40%, >45%, >50%, >55%, >60%, >65%, >70%, >75%,>80%.

In certain embodiments, the total reaction pressure in an OCM reactioncatalyzed by the catalysts is >1 atm, >1.1 atm, >1.2 atm, >1.3 atm, >1.4atm, >1.5 atm, >1.6 atm, >1.7 atm, >1.8 atm, >1.9 atm, >2 atm, >2.1atm, >2.1 atm, >2.2 atm, >2.3 atm, >2.4 atm, >2.5 atm, >2.6 atm, >2.7atm, >2.8 atm, >2.9 atm, >3.0 atm, >3.5 atm, >4.0 atm, >4.5 atm, >5.0atm, >5.5 atm, >6.0 atm, >6.5 atm, >7.0 atm, >7.5 atm, >8.0 atm, >8.5atm, >9.0 atm, >10.0 atm, >11.0 atm, >12.0 atm, >13.0 atm, >14.0atm, >15.0 atm, >16.0 atm, >17.0 atm, >18.0 atm, >19.0 atm or >20.0 atm.

In certain other embodiments, the total reaction pressure in an OCMreaction catalyzed by the catalysts ranges from about 1 atm to about 10atm, from about 1 atm to about 7 atm, from about 1 atm to about 5 atm,from about 1 atm to about 3 atm or from about 1 atm to about 2 atm.

In some embodiments, the methane partial pressure in an OCM reactioncatalyzed by the catalysts is >0.3 atm, >0.4 atm, >0.5 atm, >0.6atm, >0.7 atm, >0.8 atm, >0.9 atm, >1 atm, >1.1 atm, >1.2 atm, >1.3atm, >1.4 atm, >1.5 atm, >1.6 atm, >1.7 atm, >1.8 atm, >1.9 atm, >2.0atm, >2.1 atm, >2.2 atm, >2.3 atm, >2.4 atm, >2.5 atm, >2.6 atm, >2.7atm, >2.8 atm, >2.9 atm, >3.0 atm, >3.5 atm, >4.0 atm, >4.5 atm, >5.0atm, >5.5 atm, >6.0 atm, >6.5 atm, >7.0 atm, >7.5 atm, >8.0 atm, >8.5atm, >9.0 atm, >10.0 atm, >11.0 atm, >12.0 atm, >13.0 atm, >14.0atm, >15.0 atm, >16.0 atm, >17.0 atm, >18.0 atm, >19.0 atm or >20.0 atm.

In some embodiments, the GSHV in an OCM reaction catalyzed by thecatalystsis >20,000/hr, >50,000/hr, >75,000/hr, >100,000/hr, >120,000/hr, >130,000/hr, >150,000/hr, >200,000/hr, >250,000/hr, >300,000/hr, >350,000/hr, >400,000/hr, >450,000/hr, >500,000/hr, >750,000/hr, >1,000,000/hr, >2,000,000/hr, >3,000,000/hr,>4,000,000/hr.

In contrast to other OCM reactions, the present inventors havediscovered that OCM reactions catalyzed by the disclosed catalysts canbe performed (and still maintain high C2 yield, C2 selectivity,conversion, etc.) using O₂ sources other than pure O₂. For example, insome embodiments the O₂ source in an OCM reaction catalyzed by thedisclosed catalysts is air, enriched oxygen, pure oxygen, oxygen dilutedwith nitrogen (or another inert gas) or oxygen diluted with CO₂. Incertain embodiments, the O₂ source is O₂ dilutedby >99%, >98%, >97%, >96%, >95%, >94%, >93%, >92%, >91%, >90%, >85%, >80%, >75%, >70%, >65%, >60%, >55%, >50%, >45%, >40%, >35%, >30%, >25%, >20%, >15%, >10%, >9%, >8%, >7%, >6%, >5%, >4%, >3%, >2%or >1% with CO₂ or an inert gas, for example nitrogen.

The disclosed catalysts are also very stable under conditions requiredto perform any number of catalytic reactions, for example the OCMreaction. The stability of the catalysts is defined as the length oftime a catalyst will maintain its catalytic performance without asignificant decrease in performance (e.g., adecrease >20%, >15%, >10%, >5%, or greater than 1% in C2 yield, C2selectivity or conversion, etc.). In some embodiments, the disclosedcatalysts have stability under conditions required for the OCM reactionof >1 hr, >5 hrs, >10 hrs, >20 hrs, >50 hrs, >80 hrs, >90 hrs, >100hrs, >150 hrs, >200 hrs, >250 hrs, >300 hrs, >350 hrs, >400 hrs, >450hrs, >500 hrs, >550 hrs, >600 hrs, >650 hrs, >700 hrs, >750 hrs, >800hrs, >850 hrs, >900 hrs, >950 hrs, >1,000 hrs, >2,000 hrs, >3,000hrs, >4,000 hrs, >5,000 hrs, >6,000 hrs, >7,000 hrs, >8,000 hrs, >9,000hrs, >10,000 hrs, >11,000 hrs, >12,000 hrs, >13,000 hrs, >14,000hrs, >15,000 hrs, >16,000 hrs, >17,000 hrs, >18,000 hrs, >19,000hrs, >20,000 hrs, >1 yrs, >2 yrs, >3 yrs, >4 yrs or >5 yrs.

In some embodiments, the ratio of ethylene to ethane in an OCM reactioncatalyzed by the catalysts is better than the ratio of ethylene toethane in an OCM reaction catalyzed by a corresponding undoped catalystunder the same conditions. In some embodiments, the ratio of ethylene toethane in an OCM reaction catalyzed by the catalystsis >0.3, >0.4, >0.5, >0.6, >0.7, >0.8, >0.9, >1, >1.1, >1.2, >1.3, >1.4, >1.5, >1.6, >1.7, >1.8, >1.9, >2.0, >2.1, >2.2, >2.3, >2.4, >2.5, >2.6, >2.7, >2.8, >2.9, >3.0, >3.5, >4.0, >4.5, >5.0, >5.5, >6.0, >6.5, >7.0, >7.5, >8.0, >8.5, >9.0, >9.5,>10.0.

As noted above, the OCM reaction employing known catalysts suffers frompoor yield, selectivity, or conversion. In contrast, the presentlydisclosed catalysts posses a catalytic activity in the OCM reaction suchthat the yield, selectivity, and/or conversion is better than when theOCM reaction is catalyzed by a corresponding undoped catalyst. In oneembodiment, the disclosure provides a catalyst having a catalyticactivity such that the conversion of methane in the oxidative couplingof methane reaction is greater than at least 1.1 times, 1.25 times, 1.50times, 2.0 times, 3.0 times, or 4.0 times the conversion of methanecompared to the same reaction under the same conditions but performedwith a corresponding undoped catalyst. In other embodiments, theconversion of methane in an OCM reaction catalyzed by the catalyst isgreater than 10%, greater than 15%, greater than 20%, greater than 25%,greater than 30% greater than 40% or greater than 50%. In someembodiments the conversion of methane is determined when the catalyst isemployed as a heterogenous catalyst in the oxidative coupling of methaneat a temperature of 750° C. or less, 700° C. or less, 650° C. or less oreven 600° C. or less. The conversion of methane may also be determinedbased on a single pass of a gas comprising methane over the catalyst ormay be determined based on multiple passes over the catalyst.

In another embodiment, the disclosure provides a catalyst having acatalytic activity such that the C2 yield in the oxidative coupling ofmethane reaction is greater than at least 1.1 times, 1.25 times, 1.50times, 2.0 times, 3.0 times, or 4.0 times the C2 yield compared to thesame reaction under the same conditions but performed with acorresponding undoped catalyst. In some embodiments the C2 yield in anOCM reaction catalyzed by the catalyst is greater than 10%, greater than15%, greater than 20%, greater than 25%, greater than 30%, greater than50%, greater than 75%, or greater than 90%. In some embodiments the C2yield is determined when the catalyst is employed as a heterogenouscatalyst in the oxidative coupling of methane at a temperature of 750°C. or less, 700° C. or less, 650° C. or less or even 600° C. or less.The C2 yield may also be determined based on a single pass of a gascomprising methane over the catalyst or may be determined based onmultiple passes over the catalyst.

In another embodiment, the disclosure provides a catalyst having acatalytic activity such that the C2 selectivity in the oxidativecoupling of methane reaction is greater than at least 1.1 times, 1.25times, 1.50 times, 2.0 times, 3.0 times, or 4.0 times the C2 selectivitycompared to the same reaction under the same conditions but performedwith a corresponding undoped catalyst. In other embodiments, the C2selectivity in an OCM reaction catalyzed by the catalyst is greater than10%, greater than 20%, greater than 30%, greater than 40%, greater than50%, greater than 60%, greater than 65%, greater than 75%, or greaterthan 90%. In some embodiments the C2 selectivity is determined when thecatalyst is employed as a heterogenous catalyst in the oxidativecoupling of methane at a temperature of 750° C. or less, 700° C. orless, 650° C. or less or even 600° C. or less. The C2 selectivity mayalso be determined based on a single pass of a gas comprising methaneover the catalyst or may be determined based on multiple passes over thecatalyst.

In another embodiment, the disclosure provides a catalyst having acatalytic activity such that the selectivity for CO or CO₂ in theoxidative coupling of methane reaction is less than at least 0.9 times,0.8 times, 0.5 times, 0.2 times, or 0.1 times the selectivity for CO orCO₂ compared to the same reaction under the same conditions butperformed with a corresponding undoped catalyst.

In other embodiments, the above selectivity, conversion and yield valuesare determined at a temperature of less than 850° C., less than 800° C.,less than 750° C., less than 700° C. or less than 650° C.

In addition to air or O₂ gas, the presently disclosed catalysts andassociated methods provide for use of other sources of oxygen in the OCMreaction. In this respect, an alternate source of oxygen such a CO₂,H₂O, SO₂ or SO₃ may be used either in place of, or in addition to, airor oxygen as the oxygen source. Such methods have the potential toincrease the efficiency of the OCM reaction, for example by consuming areaction byproduct (e.g., CO₂ or H₂O) and controlling the OCM exothermas described below.

As noted above, in the OCM reaction, methane is oxidatively converted tomethyl radicals, which are then coupled to form ethane, which issubsequently oxidized to ethylene. In traditional OCM reactions, theoxidation agent for both the methyl radical formation and the ethaneoxidation to ethylene is oxygen. In order to minimize full oxidation ofmethane or ethane to carbon dioxide, i.e. maximize C2 selectivity, themethane to oxygen ratio is generally kept at 4 (i.e. full conversion ofmethane into methyl radicals) or above. As a result, the OCM reaction istypically oxygen limited and thus the oxygen concentration in theeffluent is zero.

Accordingly, in one embodiment the present disclosure provides a methodfor increasing the methane conversion and increasing, or in someembodiments, not reducing, the C2 selectivity in an OCM reaction. Thedisclosed methods include adding to a traditional OCM catalyst anotherOCM catalyst that uses an oxygen source other than molecular oxygen. Insome embodiments, the alternate oxygen source is CO₂, H₂O, SO₂, SO₃ orcombinations thereof. For example in some embodiments, the alternateoxygen source is CO₂. In other embodiments the alternate oxygen sourceis H₂O.

Because C2 selectivity is typically between 50% and 80% in the OCMreaction, OCM typically produces significant amounts of CO₂ as abyproduct (CO₂ selectivity can typically range from 20-50%).Additionally, H₂O is produced in copious amounts, regardless of the C2selectivity. Therefore both CO₂ and H₂O are attractive oxygen sourcesfor OCM in an O₂ depleted environment. Accordingly, one embodiment ofthe present disclosure provides a catalyst (and related methods for usethereof) which is catalytic in the OCM reaction and which uses CO₂, H₂O,SO₂, SO₃ or another alternative oxygen source or combinations thereof asa source of oxygen. Other embodiments, provide a catalytic materialcomprising two or more catalysts, wherein the catalytic materialcomprises at least one catalyst which is catalytic in the OCM reactionand uses O₂ for at least one oxygen source and at least one catalystswhich is catalytic in the OCM reaction and uses at least of CO₂, H₂O,SO₂, SO₃ or another alternative oxygen source. Methods for performingthe OCM reaction with such catalytic materials are also provided. Suchcatalysts comprise any of the compositions disclosed herein and areeffective as catalysts in an OCM reaction using an alternative oxygensource at temperatures of 900° C. or lower, 850° C. or lower, 800° C. orlower, 750° C. or lower, 700° C. or lower or even 650° C. or lower.

Examples of OCM catalysts that use CO₂ or other oxygen sources ratherthan O₂ include, but are not limited to, catalysts comprising La₂O₃/ZnO,CeO₂/ZnO, CaO/ZnO, CaO/CeO₂, CaO/Cr₂O₃, CaO/MnO₂, SrO/ZnO, SrO/CeO₂,SrO/Cr₂O₃, SrO/MnO₂, SrCO₃/MnO₂, BaO/ZnO, BaO/CeO₂, BaO/Cr₂O₃, BaO/MnO₂,CaO/MnO/CeO₂, Na₂WO₄/Mn/SiO₂, Pr₂O₃, or Tb₂O₃.

Some embodiments provide a method for performing OCM, wherein a mixtureof an OCM catalyst which use O₂ as an oxygen source (referred to hereinas an O₂-OCM catalyst) and an OCM catalyst which use CO₂ as an oxygensource (referred to herein as a CO₂-OCM catalyst) is employed as thecatalytic material, for example in a catalyst bed. Such methods havecertain advantages. For example, the CO₂-OCM reaction is endothermic andthe O₂-OCM reaction is exothermic, and thus if the right mixture and/orarrangement of CO₂-OCM and O₂-OCM catalysts is used, the methods areparticularly useful for controlling the exotherm of the OCM reaction. Insome embodiments, the catalyst bed comprises a mixture of O₂-OCMcatalyst and CO₂-OCM catalysts. The mixture may be in a ratio of 1:99 to99:1. The two catalysts work synergistically as the O₂-OCM catalystsupplies the CO₂-OCM catalyst with the necessary carbon dioxide and theendothermic nature of the C₂-OCM reaction serves to control the exothermof the overall reaction. Alternatively, the CO₂ source may be externalto the reaction (e.g., fed in from a CO₂ tank, or other source) and/orthe the heat required for the CO₂-OCM reaction is supplied from anexternal source (e.g., heating the reactor).

Since the gas composition will tend to become enriched in CO₂ as itflows through the catalyst bed (i.e., as the OCM reaction proceeds, moreCO₂ is produced), some embodiments of the present invention provide anOCM method wherein the catalyst bed comprises a gradient of catalystswhich changes from a high concentration of O₂-OCM catalysts at the frontof the bed to a high concentration of CO₂-OCM catalysts at the end ofthe catalyst bed.

The O₂-OCM catalyst and CO₂ OCM catalyst may have the same or differentcompositions. For example, in some embodiments the O₂-OCM catalyst andCO₂-OCM catalyst have the same composition but different morphologies(e.g., nanowire, bent nanowire, bulk, etc.). In other embodiments theO₂-OCM and the CO₂-OCM catalyst have different compositions.

Furthermore, CO₂-OCM catalysts will typically have higher selectivity,but lower yields than an O₂-OCM catalyst. Accordingly, in one embodimentthe methods comprise use of a mixture of an O₂-OCM catalyst and aCO₂-OCM catalyst and performing the reaction in O₂ deprived environmentso that the CO₂-OCM reaction is favored and the selectivity isincreased. Under appropriate conditions the yield and selectivity of theOCM reaction can thus be optimized.

In some other embodiments, the catalyst bed comprises a mixture of oneor more low temperature O₂-OCM catalyst (i.e., a catalyst active at lowtemperatures, for example less than 700° C.) and one or more hightemperature CO₂-OCM catalyst (i.e., a catalyst active at hightemperatures, for example 800° C. or higher). Here, the required hightemperature for the CO₂-OCM may be provided by the hotspots produced bythe O₂-OCM catalyst. In such a scenario, the mixture may be sufficientlycoarse such that the hotspots are not being excessively cooled down byexcessive dilution effect.

In other embodiments, the catalyst bed comprises alternating layers ofO₂-OCM and CO₂-OCM catalysts. The catalyst layer stack may begin with alayer of O₂-OCM catalyst, so that it can supply the next layer (e.g., aCO₂-OCM layer) with the necessary CO₂. The O₂-OCM layer thickness may beoptimized to be the smallest at which O2 conversion is 100% and thus theCH₄ conversion of the layer is maximized. The catalyst bed may compriseany number of catalyst layers, for example the overall number of layersmay be optimized to maximize the overall CH₄ conversion and C2selectivity.

In some embodiments, the catalyst bed comprises alternating layers oflow temperature O₂-OCM catalysts and high temperature CO₂-OCM catalysts.Since the CO₂-OCM reaction is endothermic, the layers of CO₂-OCMcatalyst may be sufficiently thin such that in can be “warmed up” by thehotspots of the O₂-OCM layers. The endothermic nature of the CO₂-OCMreaction can be advantageous for the overall thermal management of anOCM reactor. In some embodiments, the CO₂-OCM catalyst layers act as“internal” cooling for the O₂-OCM layers, thus simplifying therequirements for the cooling, for example in a tubular reactor.Therefore, an interesting cycle takes place with the endothermicreaction providing the necessary heat for the endothermic reaction andthe endothermic reaction providing the necessary cooling for theexothermic reaction.

Accordingly, one embodiment of the present invention is a method for theoxidative coupling of methane, wherein the method comprises conversionof methane to ethane and/or ethylene in the presence of a catalyticmaterial, and wherein the catalytic material comprises a bed ofalternating layers of O₂-OCM catalysts and CO₂-OCM catalysts. In otherembodiments the bed comprises a mixture (i.e., not alternating layers)of O₂-OCM catalysts and CO₂-OCM catalysts.

In other embodiments, the OCM methods include use of a jacketed reactorwith the exothermic O₂-OCM reaction in the core and the endothermicCO₂-OCM reaction in the mantel. In other embodiments, the unused CO₂ canbe recycled and reinjected into the reactor, optionally with therecycled CH₄. Additional CO₂ can also be injected to increase theoverall methane conversion and help reduce greenhouse gases.

In other embodiments, the reactor comprises alternating stages of O₂-OCMcatalyst beds and CO₂-OCM catalyst beds. The CO₂ necessary for theCO₂-OCM stages is provided by the O₂-OCM stage upstream. Additional CO₂may also be injected. The O₂ necessary for the subsequent O₂-OCM stagesis injected downstream from the CO₂-OCM stages. The CO₂-OCM stages mayprovide the necessary cooling for the O₂-OCM stages. Alternatively,separate cooling may be provided. Likewise, if necessary the inlet gasof the CO₂-OCM stages can be additionally heated, the CO₂-OCM bed can beheated or both.

In related embodiments, the CO₂ naturally occurring in natural gas isnot removed prior to performing the OCM, alternatively CO2 is added tothe feed with the recycled methane. Instead the CO₂ containing naturalgas is used as a feedstock for CO₂-OCM, thus potentially saving aseparation step. The amount of naturally occurring CO₂ in natural gasdepends on the well and the methods can be adjusted accordinglydepending on the source of the natural gas.

The foregoing methods can be generalized as a method to control thetemperature of very exothermic reactions by coupling them with anendothermic reaction that uses the same feedstock (or byproducts of theexothermic reaction) to make the same product (or a related product).This concept can be reversed, i.e. providing heat to an endothermicreaction by coupling it with an exothermic reaction. This will alsoallow a higher per pass yield in the OCM reactor.

For purpose of simplicity, the above description relating to the use ofO₂-OCM and CO₂-OCM catalysts was described in reference to the oxidativecoupling of methane (OCM); however, the same concept is applicable toother catalytic reactions including but not limited to: oxidativedehydrogenation (ODH) of alkanes to their corresponding alkenes,selective oxidation of alkanes and alkenes and alkynes, etc. Forexample, in a related embodiment, a catalyst capable of using analternative oxygen source (e.g., CO₂, H₂O, SO₂, SO₃ or combinationsthereof) to catalyze the oxidative dehydrogenation of ethane isprovided. Such catalysts, and uses thereof are described in more detailbelow.

Furthermore, the above methods are applicable for creating novelcatalysts by blending catalysts that use different reactants for thesame catalytic reactions, for example different oxidants for anoxidation reaction and at least one oxidant is a byproduct of one of thecatalytic reactions. In addition, the methods can also be generalizedfor internal temperature control of reactors by blending catalysts thatcatalyze reactions that share the same or similar products but areexothermic and endothermic, respectively. These two concepts can also becoupled together.

2. Oxidative Dehydrogenation

Worldwide demand for alkenes, especially ethylene and propylene, ishigh. The main sources for alkenes include steam cracking,fluid-catalytic-cracking and catalytic dehydrogenation. The currentindustrial processes for producing alkenes, including ethylene andpropylene, suffer from some of the same disadvantages described abovefor the OCM reaction. Accordingly, a process for the preparation ofalkenes which is more energy efficient and has higher yield,selectivity, and conversion than current processes is needed. Thecatalysts disclosed herein fulfill this need and provide relatedadvantages.

In one embodiment, the catalysts are useful for the oxidativedehydrogenation (ODH) of hydrocarbons (e.g. alkanes, alkenes, andalkynes). For example, in one embodiment the catalysts are useful in anODH reaction for the conversion of ethane or propane to ethylene orpropylene, respectively. Reaction scheme (9) depicts the oxidativedehydrogenation of hydrocarbons:C_(x)H_(y)+½O₂→C_(x)H_(y-2)+H₂O  (9)

Representative catalysts useful for the ODH reaction include, but arenot limited to any of the catalysts disclosed herein.

As noted above, improvements to the yield, selectivity, and/orconversion in the ODH reaction employing bulk catalysts are needed.Accordingly, in one embodiment, the catalysts posses a catalyticactivity in the ODH reaction such that the yield, selectivity, and/orconversion is better than when the ODH reaction is catalyzed by acorresponding undoped catalyst. In one embodiment, the disclosureprovides a catalyst having a catalytic activity such that the conversionof hydrocarbon to alkene in the ODH reaction is greater than at least1.1 times, 1.25 times, 1.50 times, 2.0 times, 3.0 times, or 4.0 timesthe conversion of methane to ethylene compared to the same reactionunder the same conditions but performed with a corresponding undopedcatalyst. In other embodiments, the conversion of alkanes in an ODHreaction catalyzed by the catalyst is greater than 10%, greater than15%, greater than 20%, greater than 25%, greater than 30%, greater than50%, greater than 75%, or greater than 90%.

In another embodiment, the disclosure provides a catalyst having acatalytic activity such that the yield of alkene in an ODH reaction isgreater than at least 1.1 times, 1.25 times, 1.50 times, 2.0 times, 3.0times, or 4.0 times the yield of ethylene compared to the same reactionunder the same conditions but performed with a corresponding undopedcatalyst. In some embodiments the yield of alkene in an ODH reactioncatalyzed by the catalyst is greater than 10%, greater than 20%, greaterthan 30%, greater than 50%, greater than 75%, or greater than 90%.

In another embodiment, the disclosure provides a catalyst having acatalytic activity such that the selectivity for alkenes in an ODHreaction is greater than at least 1.1 times, 1.25 times, 1.50 times, 2.0times, 3.0 times, or 4.0 times the selectivity for alkenes compared tothe same reaction under the same conditions but performed with acorresponding undoped catalyst. In other embodiments, the selectivityfor alkenes in an ODH reaction catalyzed by the catalyst is greater than50%, greater than 60%, greater than 70%, greater than 75%, greater than80%, greater than 85%, greater than 90%, or greater than 95%.

In another embodiment, the disclosure provides a catalyst having acatalytic activity such that the selectivity for CO or CO₂ in an ODHreaction is less than at least 0.9 times, 0.8 times, 0.5 times, 0.2times, or 0.1 times the selectivity for CO or CO₂ compared to the samereaction under the same conditions but performed with a correspondingundoped catalyst.

In one embodiment, the catalysts disclosed herein enable efficientconversion of hydrocarbon to alkene in the ODH reaction at temperaturesless than when a corresponding undoped catalyst is used. For example, inone embodiment, the catalysts disclosed herein enable efficientconversion (i.e. high yield, conversion, and/or selectivity) ofhydrocarbon to alkene at temperatures of less than 800° C., less than700° C., less than 600° C., less than 500° C., less than 400° C., orless than 300° C.

One embodiment of the present disclosure is directed to a catalystcapable of using an alternative oxygen source (e.g., CO₂, H₂O, SO₂, SO₃or combinations thereof) to catalyze the oxidative dehydrogenation ofethane. For example, the ODH reaction may proceed according to thefollowing reaction (10):CO₂+C_(x)H_(y)→C_(x)H_(y-2)+CO+H₂O  (10)wherein x is an integer and Y is 2x+2. Compositions useful in thisregard include Fe₂O₃, Cr₂O₃, MnO₂, Ga₂O₃, Cr/SiO₂, Cr/SO₄—SiO₂,Cr—K/SO₄—SiO₂, Na₂WO₄—Mn/SiO₂, Cr—HZSM-5, Cr/Si-MCM-41 (Cr—HZSM-5 andCr/Si-MCM-41 refer to known zeolites) and MoC/SiO₂. In some embodiments,any of the foregoing catalyst compositions may be supported on SiO₂,ZrO₂, Al₂O₃, TiO₂ or combinations thereof.

The catalysts having ODH activity with alternative oxygen sources (e.g.,CO₂, referred to herein as a CO₂—ODH catalyst) have a number ofadvantages. For example, in some embodiments a method for convertingmethane to ethylene comprises use of an O₂-OCM catalyst in the presenceof a CO₂—ODH catalyst is provided. Catalytic materials comprising atleast one O₂-OCM catalyst and at least one CO₂-ODH catalyst are alsoprovided in some embodiments. This combination of catalysts results in ahigher yield of ethylene (and/or ratio of ethylene to ethane) since theCO₂ produced by the OCM reaction is consumed and used to convert ethaneto ethylene.

In one embodiment, a method for preparation of ethylene comprisesconverting methane to ethylene in the presence of two or more catalysts,wherein at least one catalyst is an O₂-OCM catalyst and at least onecatalyst is a CO₂-ODH catalyst. Such methods have certain advantages.For example, the CO2-ODH reaction is endothermic and the O₂-OCM reactionis exothermic, and thus if the right mixture and/or arrangement ofCO₂-ODH and O₂-OCM catalysts is used, the methods are particularlyuseful for controlling the exotherm of the OCM reaction. In someembodiments, the catalyst bed comprises a mixture of O₂-OCM catalyst andCO2-ODH catalysts. The mixture may be in a ratio of 1:99 to 99:1. Thetwo catalysts work synergistically as the O₂-OCM catalyst supplies theCO₂-ODH catalyst with the necessary carbon dioxide and the endothermicnature of the C₂-OCM reaction serves to control the exotherm of theoverall reaction.

Since the gas composition will tend to become enriched in CO₂ as itflows through the catalyst bed (i.e., as the OCM reaction proceeds, moreCO₂ is produced), some embodiments of the present invention provide anOCM method wherein the catalyst bed comprises a gradient of catalystswhich changes from a high concentration of O₂-OCM catalysts at the frontof the bed to a high concentration of CO₂-ODH catalysts at the end ofthe catalyst bed.

The O₂-ODH catalyst and CO₂-ODH catalyst may have the same or differentcompositions. For example, in some embodiments the O₂-ODH catalyst andCO₂-ODH catalyst have the same composition but different morphologies(e.g., catalyst, bent catalyst, bulk, etc.). In other embodiments theO₂-ODH and the CO₂-ODH catalyst have different compositions.

In other embodiments, the catalyst bed comprises alternating layers ofO₂-OCM and CO₂-ODH catalysts. The catalyst layer stack may begin with alayer of O₂-OCM catalyst, so that it can supply the next layer (e.g., aCO2-ODH layer) with the necessary CO₂. The O₂-OCM layer thickness may beoptimized to be the smallest at which O2 conversion is 100% and thus theCH₄ conversion of the layer is maximized. The catalyst bed may compriseany number of catalyst layers, for example the overall number of layersmay be optimized to maximize the overall CH₄ conversion and C2selectivity.

In some embodiments, the catalyst bed comprises alternating layers oflow temperature O₂-OCM catalysts and high temperature CO₂-ODH catalysts.Since the CO₂-ODH reaction is endothermic, the layers of CO₂-ODHcatalyst may be sufficiently thin such that in can be “warmed up” by thehotspots of the O₂-OCM layers. The endothermic nature of the CO₂-ODHreaction can be advantageous for the overall thermal management of anOCM reactor. In some embodiments, the CO₂-ODH catalyst layers act as“internal” cooling for the O₂-OCM layers, thus simplifying therequirements for the cooling, for example in a tubular reactor.Therefore, an interesting cycle takes place with the endothermicreaction providing the necessary heat for the endothermic reaction andthe endothermic reaction providing the necessary cooling for theexothermic reaction.

Accordingly, one embodiment of the present invention is a method for theoxidative coupling of methane, wherein the method comprises conversionof methane to ethane and/or ethylene in the presence of a catalyticmaterial, and wherein the catalytic material comprises a bed ofalternating layers of O₂-OCM catalysts and CO₂-ODH catalysts. In otherembodiments the bed comprises a mixture (i.e., not alternating layers)of O₂-OCM catalysts and CO₂-ODH catalysts. Such methods increase theethylene yield and/or ratio of ethylene to ethane compared to otherknown methods.

In other embodiments, the OCM methods include use of a jacketed reactorwith the exothermic O₂-OCM reaction in the core and the endothermicCO₂-ODH reaction in the mantel. In other embodiments, the unused CO₂ canbe recycled and reinjected into the reactor, optionally with therecycled CH₄. Additional CO₂ can also be injected to increase theoverall methane conversion and help reduce greenhouse gases.

In other embodiments, the reactor comprises alternating stages of O₂-OCMcatalyst beds and CO₂-ODH catalyst beds. The CO₂ necessary for theCO₂-ODH stages is provided by the O₂-OCM stage upstream. Additional CO₂may also be injected. The O₂ necessary for the subsequent O2-OCM stagesis injected downstream from the CO₂-ODH stages. The CO₂-ODH stages mayprovide the necessary cooling for the O₂-OCM stages. Alternatively,separate cooling may be provided. Likewise, if necessary the inlet gasof the CO₂-ODH stages can be additionally heated, the CO₂-ODH bed can beheated or both.

In related embodiments, the CO₂ naturally occurring in natural gas isnot removed prior to performing the OCM, alternatively CO₂ is added tothe feed with the recycled methane. Instead the CO₂ containing naturalgas is used as a feedstock for CO₂-ODH, thus potentially saving aseparation step. The amount of naturally occurring CO₂ in natural gasdepends on the well and the methods can be adjusted accordinglydepending on the source of the natural gas.

3. Carbon Dioxide Reforming of Methane

Carbon dioxide reforming (CDR) of methane is an attractive process forconverting CO₂ in process streams or naturally occurring sources intothe valuable chemical product, syngas (a mixture of hydrogen and carbonmonoxide). Syngas can then be manufactured into a wide range ofhydrocarbon products through processes such as the Fischer-Tropschsynthesis (discussed below) to form liquid fuels including methanol,ethanol, diesel, and gasoline. The result is a powerful technique to notonly remove CO₂ emissions but also create a new alternative source forfuels that are not derived from petroleum crude oil. The CDR reactionwith methane is exemplified in reaction scheme (11).CO₂+CH₄→2CO+2H₂  (11)

Unfortunately, no established industrial technology for CDR exists todayin spite of its tremendous potential value. While not wishing to bebound by theory, it is thought that the primary problem with CDR is dueto side-reactions from catalyst deactivation induced by carbondeposition via the Boudouard reaction (reaction scheme (12)) and/ormethane cracking (reaction scheme (13)) resulting from the hightemperature reaction conditions. The occurrence of the coking effect isintimately related to the complex reaction mechanism, and the associatedreaction kinetics of the catalysts employed in the reaction.2CO→C+CO₂  (12)CH₄→C+2H₂  (13)

While not wishing to be bound by theory, the CDR reaction is thought toproceed through a multistep surface reaction mechanism. FIG. 3schematically depicts a CDR reaction 700, in which activation anddissociation of CH₄ occurs on the metal catalyst surface 710 to formintermediate “M-C”. At the same time, absorption and activation of CO₂takes place at the oxide support surface 720 to provide intermediate“S—CO₂”, since the carbon in a CO₂ molecule as a Lewis acid tends toreact with the Lewis base center of an oxide. The final step is thereaction between the M-C species and the activated S—CO₂ to form CO.

In one embodiment, the catalysts disclosed herein are useful ascatalysts for the carbon dioxide reforming of methane. For example, inone embodiment the catalysts are useful as catalysts in a CDR reactionfor the production of syn gas.

Improvements to the yield, selectivity, and/or conversion in the CDRreaction employing bulk catalysts are needed. Accordingly, in oneembodiment, the catalysts posses a catalytic activity in the CDRreaction such that the yield, selectivity, and/or conversion is betterthan when the CDR reaction is catalyzed by a corresponding undopedcatalyst. In one embodiment, the disclosure provides a catalyst having acatalytic activity such that the conversion of CO₂ to CO in the CDRreaction is greater than at least 1.1 times, 1.25 times, 1.50 times, 2.0times, 3.0 times, or 4.0 times the conversion of CO₂ to CO compared tothe same reaction under the same conditions but performed with acorresponding undoped catalyst. In other embodiments, the conversion ofCO₂ to CO in a CDR reaction catalyzed by the catalyst is greater than10%, greater than 15%, greater than 20%, greater than 25%, greater than30%, greater than 50%, greater than 75%, or greater than 90%.

In another embodiment, the disclosure provides a catalyst having acatalytic activity such that the yield of CO in a CDR reaction isgreater than at least 1.1 times, 1.25 times, 1.50 times, 2.0 times, 3.0times, or 4.0 times the yield of CO compared to the same reaction underthe same conditions but performed with a corresponding undoped catalyst.In some embodiments the yield of CO in a CDR reaction catalyzed by thecatalyst is greater than 10%, greater than 20%, greater than 30%,greater than 50%, greater than 75%, or greater than 90%.

In another embodiment, the disclosure provides a catalyst having acatalytic activity such that the selectivity for CO in a CDR reaction isgreater than at least 1.1 times, 1.25 times, 1.50 times, 2.0 times, 3.0times, or 4.0 times the selectivity for CO compared to the same reactionunder the same conditions but performed with a corresponding undopedcatalyst. In other embodiments, the selectivity for CO in a CDR reactioncatalyzed by the catalyst is greater than 10%, greater than 20%, greaterthan 30%, greater than 40%, greater than 50%, greater than 65%, greaterthan 75%, or greater than 90%.

In one embodiment, the catalysts disclosed herein enable efficientconversion of CO₂ to CO in the CDR reaction at temperatures less thanwhen a corresponding undoped catalyst. For example, in one embodiment,the catalysts enable efficient conversion (i.e., high yield, conversion,and/or selectivity) of CO₂ to CO at temperatures of less than 900° C.,less than 800° C., less than 700° C., less than 600° C., or less than500° C.

4. Fischer-Tropsch Synthesis

Fischer-Tropsch synthesis (FTS) is a valuable process for convertingsynthesis gas (i.e., CO and H₂) into valuable hydrocarbon fuels, forexample, light alkenes, gasoline, diesel fuel, etc. FTS has thepotential to reduce the current reliance on the petroleum reserve andtake advantage of the abundance of coal and natural gas reserves.Current FTS processes suffer from poor yield, selectivity, conversion,catalyst deactivation, poor thermal efficiency and other relateddisadvantages. Production of alkanes via FTS is shown in reaction scheme(14), wherein n is an integer.CO+2H₂→(1/n)(C_(n)H_(2n))+H₂O  (14)

In one embodiment, the catalysts are useful as catalysts in FTSprocesses. For example, in one embodiment the catalysts are useful ascatalysts in a FTS process for the production of alkanes.

Improvements to the yield, selectivity, and/or conversion in FTSprocesses employing bulk catalysts are needed. Accordingly, in oneembodiment, the catalysts posses a catalytic activity in an FTS processsuch that the yield, selectivity, and/or conversion is better than whenthe FTS process is catalyzed by a corresponding undoped catalyst. In oneembodiment, the disclosure provides a catalyst having a catalyticactivity such that the conversion of CO to alkane in an FTS process isgreater than at least 1.1 times, 1.25 times, 1.50 times, 2.0 times, 3.0times, or 4.0 times the conversion of CO to alkane compared to the samereaction under the same conditions but performed with a correspondingundoped catalyst. In other embodiments, the conversion of CO to alkanein an FTS process catalyzed by the catalyst is greater than 10%, greaterthan 15%, greater than 20%, greater than 25%, greater than 30%, greaterthan 50%, greater than 75%, or greater than 90%.

In another embodiment, the disclosure provides a catalyst having acatalytic activity such that the yield of alkane in a FTS process isgreater than at least 1.1 times, 1.25 times, 1.50 times, 2.0 times, 3.0times, or 4.0 times the yield of alkane compared to the same reactionunder the same conditions but performed with a corresponding undopedcatalyst. In some embodiments the yield of alkane in an FTS processcatalyzed by the catalyst is greater than 10%, greater than 20%, greaterthan 30%, greater than 40%, greater than 50%, greater than 65%, greaterthan 75%, or greater than 90%.

In another embodiment, the disclosure provides a catalyst having acatalytic activity such that the selectivity for alkanes in an FTSprocess is greater than at least 1.1 times, 1.25 times, 1.50 times, 2.0times, 3.0 times, or 4.0 times the selectivity for alkanes compared tothe same reaction under the same conditions but performed with acorresponding undoped catalyst. In other embodiments, the selectivityfor alkanes in an FTS process catalyzed by the catalyst is greater than10%, greater than 20%, greater than 30%, greater than 50%, greater than75%, or greater than 90%.

In one embodiment, the catalysts disclosed herein enable efficientconversion of CO to alkanes in a CDR process at temperatures less thanwhen a corresponding undoped catalyst is used. For example, in oneembodiment, the catalysts enable efficient conversion (i.e., high yield,conversion, and/or selectivity) of CO to alkanes at temperatures of lessthan 400° C., less than 300° C., less than 250° C., less than 200° C.,less the 150° C., less than 100° C. or less than 50° C.

5. Oxidation of CO

Carbon monoxide (CO) is a toxic gas and can convert hemoglobin tocarboxyhemoglobin resulting in asphyxiation. Dangerous levels of CO canbe reduced by oxidation of CO to CO₂ as shown in reaction scheme 15:CO+1/2O₂→CO₂  (15)

Catalysts for the conversion of CO into CO₂ have been developed butimprovements to the known catalysts are needed. Accordingly in oneembodiment, the present disclosure provides catalysts useful ascatalysts for the oxidation of CO to CO_(2.)

In one embodiment, the catalysts posses a catalytic activity in aprocess for the conversion of CO into CO₂ such that the yield,selectivity, and/or conversion is better than when the oxidation of COinto CO₂ is catalyzed by a corresponding undoped catalyst. In oneembodiment, the disclosure provides a catalyst having a catalyticactivity such that the conversion of CO to CO₂ is greater than at least1.1 times, 1.25 times, 1.50 times, 2.0 times, 3.0 times, or 4.0 timesthe conversion of CO to CO₂ compared to the same reaction under the sameconditions but performed with a corresponding undoped catalyst. In otherembodiments, the conversion of CO to CO₂ catalyzed by the catalyst isgreater than 10%, greater than 15%, greater than 20%, greater than 25%,greater than 30%, greater than 50%, greater than 75%, or greater than90%.

In another embodiment, the disclosure provides a catalyst having acatalytic activity such that the yield of CO₂ from the oxidation of COis greater than at least 1.1 times, 1.25 times, 1.50 times, 2.0 times,3.0 times, or 4.0 times the yield of CO₂ compared to the same reactionunder the same conditions but performed with a corresponding undopedcatalyst. In some embodiments the yield of CO₂ from the oxidation of COcatalyzed by the catalyst is greater than 10%, greater than 20%, greaterthan 30%, greater than 50%, greater than 75%, or greater than 90%.

In another embodiment, the disclosure provides a catalyst having acatalytic activity such that the selectivity for CO₂ in the oxidation ofCO is greater than at least 1.1 times, 1.25 times, 1.50 times, 2.0times, 3.0 times, or 4.0 times the selectivity for CO₂ compared to thesame reaction under the same conditions but performed with acorresponding undoped catalyst. In other embodiments, the selectivityfor CO₂ in the oxidation of CO catalyzed by the catalyst is greater than10%, greater than 20%, greater than 30%, greater than 40%, greater than50%, greater than 65%, greater than 75%, or greater than 90%.

In one embodiment, the catalysts disclosed herein enable efficientconversion of CO to CO₂ at temperatures less than when a correspondingundoped catalyst is used as a catalyst. For example, in one embodiment,the catalysts enable efficient conversion (i.e., high yield, conversion,and/or selectivity) of CO to CO₂ at temperatures of less than 500° C.,less than 400° C., less than 300° C., less than 200° C., less than 100°C., less than 50° C. or less than 20° C.

Although various reactions have been described in detail, the disclosedcatalysts are useful as catalysts in a variety of other reactions. Ingeneral, the disclosed catalysts find utility in any reaction utilizinga heterogeneous catalyst and have a catalytic activity such that theyield, conversion, and/or selectivity in reaction catalyzed by thecatalysts is better than the yield, conversion and/or selectivity in thesame reaction catalyzed by a corresponding undoped catalyst.

6. Evaluation of Catalytic Properties

To evaluate the catalytic properties of the catalysts in a givenreaction, for example those reactions discussed above, various methodscan be employed to collect and process data including measurements ofthe kinetics and amounts of reactants consumed and the products formed.In addition to allowing for the evaluation of the catalyticperformances, the data can also aid in designing large scale reactors,experimentally validating models and optimizing the catalytic process.

One exemplary methodology for collecting and processing data is depictedin FIG. 4. Three main steps are involved. The first step (block 750)comprises the selection of a reaction and catalyst. This influences thechoice of reactor and how it is operated, including batch, flow, etc.(block 754). Thereafter, the data of the reaction are compiled andanalyzed (block 760) to provide insights to the mechanism, rates andprocess optimization of the catalytic reaction. In addition, the dataprovide useful feed backs for further design modifications of thereaction conditions. Additional methods for evaluating catalyticperformance in the laboratory and industrial settings are described in,for example, Bartholomew, C. H. et al. Fundamentals of IndustrialCatalytic Processes, Wiley-AlChE; 2Ed (1998).

As an example, in a laboratory setting, an Altamira Benchcat 200 can beemployed using a 4 mm ID diameter quartz tube with a 0.5 mm ID capillarydownstream. Catalysts are tested in a number of different dilutions andamounts. In some embodiments, the range of testing is between 10 and 300mg. In some embodiments, the catalysts are diluted with quartz (SiO₂) orone of the other support materials disclosed above to minimize hot spotsand provide an appropriate loading into the reactor.

In a typical procedure, 100 mg is the total charge of catalyst,optionally including quartz sand. On either side of the catalysts asmall plug of glass wool is loaded to keep the catalysts in place. Athermocouple is placed on the inlet side of the catalyst bed into theglass wool to monitor the temperature at the catalyst bed. Anotherthermocouple can be placed on the downstream end of the catalyst bed tomeasure the exotherms, if any.

When blending the catalyst with quartz silica, the following exemplaryprocedure may be used: x (usually 10-50) mg of the catalyst, for examplea magnesium oxide based catalyst, is blended with (100−x) mg of quartz(SiO₂). Thereafter, about 2 ml of ethanol or water is added to form aslurry mixture, which is then sonicated for about 10 minutes. The slurryis then dried in an oven at about 140° C. for 2 hours to remove solvent.The resulting solid mixture is then scraped out and loaded into thereactor between the plugs of quartz wool.

Once loaded into the reactor, the reactor is inserted into the Altamirainstrument and furnace and then a temperature and flow program isstarted. In some embodiment, the total flow is 50 to 100 sccm of gasesbut this can be varied and programmed with time. In one embodiment, thetemperatures range from 500° C. to 900° C. The reactant gases compriseoxygen (diluted with nitrogen) and methane in the case of the OCMreaction and gas mixtures comprising ethane and/or propane with oxygenfor oxidative dehydrogenation (ODH) reactions. Other gas mixtures areused for other reactions.

The primary analysis of these oxidation catalysis runs is the GasChromatography (GC) analysis of the feed and effluent gases. From theseanalyses, the conversion of the oxygen and alkane feed gases can easilybe attained and estimates of yields and selectivities of the productsand by-products can be determined.

The GC method developed for these experiments employs 4 columns and 2detectors and a complex valve switching system to optimize the analysis.Specifically, a flame ionization detector (FID) is used for the analysisof the hydrocarbons only. It is a highly sensitive detector thatproduces accurate and repeatable analysis of methane, ethane, ethylene,propane, propylene and all other simple alkanes and alkenes up to fivecarbons in length and down to ppm levels.

There are two columns in series to perform this analysis, the first is astripper column (alumina) which traps polar materials (including thewater by-product and any oxygenates generated) until back-flushed laterin the cycle. The second column associated with the FID is a capillaryalumina column known as a PLOT column which performs the actualseparation of the light hydrocarbons. The water and oxygenates are notanalyzed in this method.

For the analysis of the light non-hydrocarbon gases, a ThermalConductivity Detector (TCD) may be employed which also employees twocolumns to accomplish its analysis. The target molecules for thisanalysis are CO₂, ethylene, ethane, hydrogen, oxygen, nitrogen, methaneand CO. The two columns used here are a porous polymer column known asthe Hayes Sep N which performs some of the separation for the CO₂,ethylene and ethane. The second column is a molecular sieve column whichuses size differentiation to perform the separation. It is responsiblefor the separation of H₂, O₂, N₂, methane and CO.

There is a sophisticated and timing sensitive switching between thesetwo columns in the method. In the first 2 minutes or so, the two columnsare operating in series but at about 2 minutes, the molecular sievecolumn is by-passed and the separation of the first 3 components iscompleted. At about 7 minutes, the columns are then placed back inseries and the light gases come off of the sieve according to theirmolecular size.

The end result is an accurate analysis of all of the aforementionedcomponents from these fixed beds, gas phase reactions. Analysis of otherreactions and gases not specifically described above can be performed ina similar manner known to those of skill in the art.

7. Downstream Products

As noted above, the catalysts disclosed herein are useful in reactionsfor the preparation of a number of valuable hydrocarbon compounds. Forexample, in one embodiment the catalysts are useful for the preparationof ethylene from methane via the OCM reaction. In another embodiment,the catalysts are useful for the preparation of ethylene or propylenevia oxidative dehydrogenation of ethane or propane respectively.Ethylene and propylene are valuable compounds which can be convertedinto a variety of consumer products. For example, as shown in FIG. 5,ethylene can be converted into many various compounds including lowdensity polyethylene, high density polyethylene, ethylene dichloride,ethylene oxide, ethylbenzene, linear alcohols, vinyl acetate, alkanes,alpha olefins, various hydrocarbon-based fuels, ethanol and the like.These compounds can then be further processed using methods well knownto one of ordinary skill in the art to obtain other valuable chemicalsand consumer products (e.g. the downstream products shown in FIG. 5).Propylene can be analogously converted into various compounds andconsumer goods including polypropylenes, propylene oxides, propanol, andthe like.

Accordingly, in one embodiment the invention is directed to a method forthe preparation of C2 hydrocarbons via the OCM reaction, the methodcomprises contacting a catalyst as described herein with a gascomprising methane. In some embodiments the C2 hydrocarbons are selectedfrom ethane and ethylene. In other embodiments the disclosure provides amethod of preparing downstream products of ethylene. The methodcomprises converting ethylene into a downstream product of ethylene,wherein the ethylene has been prepared via a catalytic reactionemploying a catalyst disclosed herein (e.g., OCM). In some embodiments,the downstream product of ethylene is low density polyethylene, highdensity polyethylene, ethylene dichloride, ethylene oxide, ethylbenzene,ethanol or vinyl acetate. In other embodiments, the downstream productof ethylene is natural gasoline. In still other embodiments, thedownstream product of ethylene comprises 1-hexene, 1-octene, hexane,octane, benzene, toluene, xylene or combinations thereof.

In another embodiment, a process for the preparation of ethylene frommethane comprising contacting a mixture comprising oxygen and methane ata temperature below 900° C., below 850° C., below 800° C., below 750°C., below 700° C. or below 650° C. with a catalyst as disclosed hereinis provided.

In another embodiment, the disclosure provides a method of preparing aproduct comprising low density polyethylene, high density polyethylene,ethylene dichloride, ethylene oxide, ethylbenzene, ethanol or vinylacetate or combinations thereof. The method comprises convertingethylene into low density polyethylene, high density polyethylene,ethylene dichloride, ethylene oxide, ethylbenzene, ethanol or vinylacetate, wherein the ethylene has been prepared via a catalytic reactionemploying a catalyst disclosed herein.

In more specific embodiments of the above methods, the ethylene isproduced via an OCM or ODH reaction.

In one particular embodiment, the disclosure provides a method ofpreparing a downstream product of ethylene and/or ethane. For example,the downstream product of ethylene may be a hydrocarbon fuel such asnatural gasoline or a C₄-C₁₄ hydrocarbon, including alkanes, alkenes andaromatics. Some specific examples include 1-butene, 1-hexene, 1-octene,hexane, octane, benzene, toluene, xylenes and the like. The methodcomprises converting methane into ethylene, ethane or combinationsthereof by use of a catalyst, for example any of the catalysts disclosedherein, and further oligomerizing the ethylene and/or ethane to preparea downstream product of ethylene and/or ethane. For example, the methanemay be converted to ethylene, ethane or combinations thereof via the OCMreaction as discussed above.

As depicted in FIG. 6, the method begins with charging methane (e.g., asa component in natural gas) into an OCM reactor. The OCM reaction maythen be performed utilizing a catalyst under any variety of conditions.Water and CO₂ are optionally removed from the effluent and unreactedmethane is recirculated to the OCM reactor.

Ethylene is recovered and charged to an oligomerization reactor.Optionally the ethylene stream may contain CO₂, H₂O, N₂, ethane, C3'sand/or higher hydrocarbons. Oligomerization to higher hydrocarbons(e.g., C₄-C₁₄) then proceeds under any number of conditions known tothose of skill in the art. For example oligomerization may be effectedby use of any number of catalysts known to those skilled in the art.Examples of such catalysts include catalytic zeolites, crystallineborosilicate molecular sieves, homogeneous metal halide catalysts, Crcatalysts with pyrrole ligands or other catalysts. Exemplary methods forthe conversion of ethylene into higher hydrocarbon products aredisclosed in the following references: Catalysis Science & Technology(2011), 1(1), 69-75; Coordination Chemistry Reviews (2011), 255(7-8),861-880; Eur. Pat. Appl. (2011), EP 2287142 A1 20110223; Organometallics(2011), 30(5), 935-941; Designed Monomers and Polymers (2011), 14(1),1-23; Journal of Organometallic Chemistry 689 (2004) 3641-3668;Chemistry—A European Journal (2010), 16(26), 7670-7676; Acc. Chem. Res.2005, 38, 784-793; Journal of Organometallic Chemistry, 695 (10-11):1541-1549 May 15 2010; Catalysis Today Volume 6, Issue 3, January 1990,Pages 329-349; U.S. Pat. No. 5,968,866; U.S. Pat. No. 6,800,702; U.S.Pat. No. 6,521,806; U.S. Pat. No. 7,829,749; U.S. Pat. No. 7,867,938;U.S. Pat. No. 7,910,670; U.S. Pat. No. 7,414,006 and Chem. Commun.,2002, 858-859, each of which are hereby incorporated in their entiretyby reference.

In certain embodiments, the exemplary OCM and oligomerization modulesdepicted in FIG. 6 may be adapted to be at the site of natural gasproduction, for example a natural gas field. Thus the natural gas can beefficiently converted to more valuable and readily transportablehydrocarbon commodities without the need for transport of the naturalgas to a processing facility.

Referring to FIG. 6, “natural gasoline” refers to a mixture ofoligomerized ethylene products. In this regard, natural gasolinecomprises hydrocarbons containing 5 or more carbon atoms. Exemplarycomponents of natural gasoline include linear, branched or cyclicalkanes, alkenes and alkynes, as well as aromatic hydrocarbons. Forexample, in some embodiments the natural gasoline comprises 1-pentene,1-hexene, cyclohexene, 1-octene, benzene, toluene, dimethyl benzene,xylenes, napthalene, or other oligomerized ethylene products orcombinations thereof. In some embodiments, natural gasoline may alsoinclude C3 and C4 hydrocarbons dissolved within the liquid naturalgasoline. This mixture finds particular utility in any number ofindustrial applications, for example natural gasoline is used asfeedstock in oil refineries, as fuel blend stock by operators of fuelterminals, as diluents for heavy oils in oil pipelines and otherapplications. Other uses for natural gasoline are well-known to those ofskill in the art.

The following examples are provided for purposes of illustration, notlimitation.

EXAMPLES Example 1 Preparation of a Catalyst Comprising La, Nd and Sr

Equimolar aqueous solutions of strontium nitrate, neodymium nitrate, andlanthanum nitrate were prepared. Aliquots of each solution were mixedtogether to prepare a desired formulation of La_(x)Nd_(y)Sr_(z) wherex,y,z represent mole fractions of total metal content in moles.Representative examples of formulations are: La₅₀Nd₃₀Sr₂₀, La₅₂Nd₄₅Sr₀₅,La₇₅Nd₂₂Sr₀₃, and the like. A solution of citric acid was added to themetal salt mixture so that citric acid mole/metal mole ratio was 3:1.Ethylene glycol was then added to the citric acid/metal salt solution sothat the ethylene glycol/citric acid mole ratio was 1:1. The solutionwas stirred at room temperature for 1 h. The solution was placed in a130° C. oven for 15 h to remove water and to promote resin formation.After 15 h, a hard dark resin was observed. The resin was placed in afurnace and heated to 500° C. for 8 h. The remaining material was heatedto 650° C. for 2 h to yield the desired product.

Other catalysts are prepared according to an analogous procedure. Forexample, catalysts comprising La and Sm as well as catalysts comprisingLa and Ce can be prepared according to the above general procedure.Furthermore, catalysts comprising La/Ce/Nd/Sr, La/Bi/Sr, Nd/Sr, La/Sr,La/Bi/Ce/Nd/Sr can also be prepared in this manner.

Catalysts comprising support materials can also be prepared bycoprecipitation according to the above method. For example, rare earthoxides on on MgO, CaO or AlPO₄ supports can be prepared. Specificexamples include, Nd/Sr/CaO (i.e., a catalyst comprising Nd and Sr on aCaO support).

Example 2 Preparation of a Sr Doped Nd₂O₃ Catalyst

To prepare this catalyst at a level of 20 mole % Sr (based on totalmoles of Nd₂O₃), 3.0 g of Nd₂O3 bulk from Alfa Chemicals was slurried ina solution formed by dissolving 0.378 g of Sr(NO₃)₂ in about 20 ml of DIwater. The slurry was stirred at room temperature for about 30 minutesto ensure that the Sr(NO₃)₂ dissolved. The slurry was then moved to anevaporating dish and placed into an oven at 100-140° C. for 2-3 hours toensure dryness. The solids were then calcined in a furnace by ramping upto 350° C. at 5° C./min and holding for 2 hours and then ramping againat the same rate to 700° C. and holding for 4 hours. It was then cooledto room temperature, ground and sieved to a particle size range of 180μm to 250 μm.

Example 3 Preparation of a LiMgMnB Catalyst

The following fine powders were mixed together: 1.072 g of Mn2O3 (325mesh); 1.418 g of MgO (325 mesh); 0.384 g Boric acid powder and 0.164 gLiOH anhydrous. This corresponds to an approximate molar ratio ofLi:B:Mn:Mg of 1:1:2:5. The powders were then added to about 20 ml ofwater, resulting in a black slurry. This slurry was stirred for about anhour to dissolve all of the LiOH and boric acid and then dried forseveral hours at about 120° C. In a crucible, the resulting powder wasground as fine as possible and calcined according to the followingschedule. Ramp to 350° C. at 5° C./min and hold for 120 minutes. Ramp to950° C. at 5° C./min and hold for at least 8 hours. Cool to roomtemperature and repeat grinding. In certain embodiments, the catalystwas sieved to between 150-300 μm to minimize pressure drop and then thecatalyst was ready for catalyst testing.

Example 4 Preparation of Doped LiMgMnB Catalysts

Four doped samples of the LiMgMnB catalyst prepared according to Example3 were prepared as follows:

1. 1.00 g (+−0.1 g) of uncalcined LiMgMnB were weighed into a smallbeaker. 0.060 g (+−0.01 g) of NaCl and 0.240 g of cobalt chloride wereadded to this beaker. Approximately 15 ml of DI water was added and theresulting slurry was stirred for 20 minutes. The slurry was placed in aceramic evaporating dish (small) and dried in an oven at about 110-140°C. overnight.

2. Sample 2 was prepared in a manner analogous to sample one, exceptthat 0.060 g of cobalt chloride was used.

3. Sample 3 was prepared in a manner analogous to sample one, exceptthat 0.015 g (+−0.01 g) NaCl was used.

4. Sample 4 was prepared in a manner analogous to sample one, exceptthat 0.015 g (+−0.01 g) NaCl and 0.060 g of cobalt chloride were used.

After the 4 dishes were dry, they were placed in the muffle furnace andprogrammed to run at 350° C. for 2 hours followed by 650° C. for 2 hoursfollowed by 950° C. for 8 hours before cooling to near room temperature.After cooling the dishes, the solids were ground with a pestle in thedish and run through a Gilson sieve shaker. The sieves used were, fromtop to bottom, 300 um, 212 μm, 106 μm and 75 μm. The 106 fraction wascollected and put in a vial, and the combined other fractions wereplaced in another vial.

Example 5 Preparation of NaMnW Catalysts

0.2 g of Davisil 645 Silica was mixed with 0.0365 g of Manganese nitratetetrahydrate (Mn(NO₃)₂) and 0.0179 g of Sodium tungstate (Na₂WO₄) in abeaker with enough water to make a stirrable slurry. The mixture wasstirred on a hotplate at about 60-80° C. for 3 hours, adding water asnecessary to keep from drying. The resultant slurry was placed in a100-140° C. oven overnight to dry prior to calcining in a ceramicevaporating dish with the following schedule: ramp 5° C./min to 400° C.and hold for 2 hours, ramp 5° C./min to 850° C. and hold for 8 hours.

0.410 g of ZrO₂ powder were mixed with 0.0365 g of Manganese nitratetetrahydrate (Mn(NO₃)₂) and 0.0179 g of Sodium tungstate (Na₂WO₄) in abeaker with enough water to make a stirrable slurry. The mixture wasstirred on hotplate at about 60-80° C. for 3 hours, adding water asnecessary to keep from drying. The resultant slurry was placed in a100-140° C. oven overnight to dry prior to calcining in a ceramicevaporating dish with the following schedule: ramp 5° C./min to 400° C.and hold for 2 hours, ramp 5° C./min to 850° C. and hold for 8 hours.

Example 6 OCM Catalyzed with LiMnMgB Mixed Oxide and Na—Co Doped LiMnMgBMixed Oxide

50 mg of prepared samples from examples 3 and 4 were placed into areactor tube (4 mm ID diameter quartz tube with a 0.5 mm ID capillarydownstream), which was then tested in an Altamira Benchcat 200. The gasflows were held constant at 46 sccm methane and 54 sccm air, whichcorrespond to a CH₄/O₂ ratio of 4 and a feed gas-hour space velocity(GHSV) of about 130000 h⁻¹. The reactor temperature was varied from 700°C. to 750° C. in a 50° C. increment and from 750° C. to 875° C. in 25°C. increments. The vent gases were analyzed with gas chromatography (GC)at each temperature level. FIG. 7 shows the onset of OCM between 700° C.and 750° C. for the Na/Co doped LiMnMgB mixed oxide sample whereas theonset of the OCM is between 800° C. and 825° C. for the undoped LiMnMgBmixed oxide catalyst. The C2 selectivity, methane conversion and C2yield at 750° C. for the doped catalyst were 57%, 22% and 12%,respectively. The undoped LiMnMgB mixed oxide catalyst reached 12% C2yield at 850° C.

Example 7 OCM Using a NaMnWO₄ Catalyst Supported on Silica or Zirconia

50 mg of each sample from example 5 were placed into a reactor tube (4mm ID diameter quartz tube with a 0.5 mm ID capillary downstream), whichwas then tested in an Altamira Benchcat 200. The gas flows were heldconstant at 46 sccm methane and 54 sccm air, which correspond to aCH₄/O₂ ratio of 4 and a feed gas-hour space velocity (GHSV) of about130000 h⁻¹. The reactor temperature was varied from 650° C. to 900° C.in a 50° C. increment. The vent gases were analyzed with gaschromatography (GC) at each temperature level. FIG. 8 shows the onset ofOCM between 700° C. and 750° C. for the NaMnWO₄ supported on Zirconiawhereas the onset of the OCM is between 750° C. and 800° C. for theNaMnWO₄ supported on Silica. The C2 selectivity, methane conversion andC2 yield at 750° C. for the Zirconia supported catalyst were 45%, 20%and 9%, respectively.

Example 8 High Throughput Screening of OCM Catalyzed by CatalystLibraries

The effect of doping of bulk rare earth oxides or other mixed oxides wasevaluated by preparing libraries of doped catalysts on a quartz waferetched to form a 16×16 well area (4 ml per well) in which about 1 mg ofthe base catalyst (e.g., bulk rare earth oxide) is added. These oxideswere first suspended in slurries with Butanol then the slurries weredistributed to the wells using automated liquid dispensing. The waferlibrary was then dried.

Aqueous salt solutions of 49 different metals were prepared and added tothe wells in a pre-set pattern design with 4 repeats of each doping in 4different area of the wafer. The list of metal salts evaluated was asfollows: Al(NO₃)₃, CuCl, CsCl, BaCl₂, CeCl₃, Ga(NO₃)₃, InCl₃, HfCl₂O,Fe(NO₃)₃, CrCl₃, LaCl₃, RuCl₃, SmCl₃, EuCl₃, YCl₃, Sr(NO₃)₂, ZrOCl₂,TaCl₅, RhAcAc, Be(NO₃)₂, AuCl₄H, NaCl, NiCl₂, CoCl₂, SbCl₃, Ba(NO₃)₂,VCl₃, PrCl₃, AgNO₃, TeCl₄, ErCl₃, Tb(NO₃)₃, HfCl₂O, NaO₄W, IrCl₃,Mn(NO₃)₂, Gd(NO₃)₃, LiOH, Rb(NO₃), Ca(NO₃)₂, Lu(NO₃)₃, KNO₃, Yb(NO₃)₃,H₃BO₃, (NH₄)₆Mo₇O₂₄, ScCl₃, NdCl₃, Pd(NO₃)₂, Mg(NO₃)₂, Te(OH)₄,(NH₄)₂TiO(C₂O₄)₂, NbCl₅

The wafer was calcined again after doping at 700° C. for 4 hours.Testing of the activity of the doped catalysts was conducted in aScanning Mass Spectrometer, which allows to heat up at set temperatureindividual wells on the wafer while flowing a reactant mixture on top ofthe heated well. Reaction products were aspirated through a glasscapillary and analysed using a mass spectrometer. The gas mixture incontact with the catalytic material was comprised of Methane, Oxygen,Argon with a 4/1/1 molar ratio.

The products analysed with the mass spectrometer were: H₂O, CO₂, CO,C₂H₆, C₂H₄, CH₄ and O₂. Test temperatures were typically varied from600° C. to 800° C. in 50° C. increment with a one minute hold at eachtemperature.

In the following examples the relative Ethane and CO₂ concentrations areplotted for the gas effluent collected at different temperatures fordifferent catalyst compositions. These graphs provide the ability toquickly compare the activity and selectivity of multiple catalystswithin a catalyst library. The higher the ethane concentration at agiven CO₂ concentration the more selective the catalyst is. The lowerthe CO₂ concentration at a given ethane concentration the more selectivethe catalyst is. The undoped samples results are shown in grey forcomparison in FIGS. 10 to 14 for comparison.

Example 8-a

Doped Co/Na/LiMnMgB library. A SMS wafer with a base oxide from example4-1 was prepared and tested as described above. The results of the testare presented in FIG. 9. Be, Ba, Al, Hf dopants were found to promotethe Co/Na/LiMnMgB catalyst activity further without affecting theselectivity towards higher hydrocarbons.

Example 8-b

Doping of MnW on Silica library. A SMS wafer with a silica supportedoxide from Example 5 was prepared and tested as described above. Theresults of the test are presented in FIG. 10. Mo, Be, Ba, Te dopantswere found to promote the OCM activity of the MnW on Silica catalyst.

Example 8-c

Doping of Nd₂O₃ library. A SMS wafer with bulk Nd₂O₃ was prepared andtested as described above. The results of the test are presented in FIG.11. Ca, Li, Na, Rb, Sm, Sr dopants were found to promote the OCMactivity of the Nd₂O₃ catalyst and improved higher hydrocarbonselectivity compared to undoped Nd₂O₃ catalyst tested under the sameconditions.

Example 8-d

Doping of Yb₂O₃ library. A SMS wafer with bulk Yb₂O₃ was prepared andtested as described above. The results of the test are presented in FIG.12. Ba, Ca, Sr dopants were found to promote the OCM activity of theYb₂O₃ catalyst and improved higher hydrocarbon selectivity compared toundoped Yb₂O₃ catalyst tested under the same conditions.

Example 8-e

Doping of Eu2O3 library. A SMS wafer with bulk Eu₂O₃ was prepared andtested as described above. The results of the test are presented in FIG.13. Na, Ba, Gd, Sm dopants were found to promote the OCM activity of theEu₂O₃ catalyst compared to undoped Eu₂O₃ catalyst tested under the sameconditions.

Example 8-f

Doping of La₂O₃ library. A SMS wafer with bulk La₂O₃ was prepared andtested as described above. The results of the test are presented in FIG.14. Ca, Sr, Nd, Hf dopants were found to promote the OCM activity of theLa₂O₃ catalyst compared to undoped La₂O₃ catalyst tested under the sameconditions. In addition to the list of OCM activators, Rh, Fe, Pr, Mn,Ir doping was found to promote unselective oxidation of methane whereasBa, Te, V, Li doping was found to suppress methane activation.

Example 9 OCM Activity of Various Catalysts

Exemplary catalysts comprising La₂O₃, Nd₂O₃ or La₃NdO₆ with one, two,three or four different dopants selected from Eu, Na, Sr, Ho, Tm, Zr,Ca, Mg, Sm, W, La, K, Ba, Zn, and Li, were prepared and tested for theirOCM activity according to the general procedures described in the aboveexamples. Each of the exemplary catalysts produced a C2 yield above 10%,a C2 selectivity above 50%, and a CH₄ conversion above 20%, when testedas OCM catalysts at 650° C. or lower at pressures ranging from 1 to 10atm.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet, areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments. These and other changes can be made to the embodiments inlight of the above-detailed description. In general, in the followingclaims, the terms used should not be construed to limit the claims tothe specific embodiments disclosed in the specification and the claims,but should be construed to include all possible embodiments along withthe full scope of equivalents to which such claims are entitled.Accordingly, the claims are not limited by the disclosure.

The invention claimed is:
 1. A method for the preparation of ethane,ethylene or combinations thereof, the method comprising contacting acatalyst with a gas comprising methane, the catalyst comprising: theformula Ln1_(4-x)Ln2_(x)O₆, wherein Ln1 and Ln2 are each independently adifferent lanthanide element, and x is a number ranging from greaterthan 0 to less than 4; and at least one doping element from groups 1-16,lanthanides, actinides or combinations thereof, wherein the catalystfurther comprises a C₂ selectivity of greater than 50% and a methaneconversion of greater than 20% when the catalyst is employed as aheterogeneous catalyst in the oxidative coupling of methane at atemperature of 750° C. or less.
 2. The method of claim 1, wherein the atleast one doping element is selected from groups 1-4, 8, 13, 14,lanthanides, actinides and combinations thereof.
 3. The method of claim1, wherein the at least one doping element is selected from groups 1-6,8, 11, 13-15, lanthanides, actinides and combinations thereof.
 4. Themethod of claim 1, wherein the at least one doping element is a rareearth element.
 5. The method of claim 1, wherein the at least one dopingelement is Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf,Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi,Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn,Ir, As, Li, Tb, Er, Te or Mo.
 6. The method of claim 1, wherein thecatalyst comprises a combination of at least two different dopingelements.
 7. The method of claim 6, wherein the two different dopingelements are selected from Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu,Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu,Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh,Ti, V, Cr, Mn, Ir, As, Li, Tb, Er, Te and Mo.
 8. The method of claim 6,wherein the combination of at least two different doping elements isLa/Nd, La/Sm, La/Ce, La/Sr, Eu/Na, Eu/Gd, Ca/Na, Eu/Sm, Eu/Sr, Mg/Sr,Ce/Mg, Gd/Sm, Sr/W, Sr/Ta, Au/Re, Au/Pb, Bi/Hf, Sr/Sn or Mg/N, Ca/S,Rb/S, Sr/Nd, Eu/Y, Mg/Nd, Sr/Na, Nd/Mg, La/Mg, Yb/S, Mg/Na, Sr/W, K/La,K/Na, Li/Cs, Li/Na, Zn/K, Li/K, Rb/Hf, Ca/Cs, Hf/Bi, Sr/Sn, Sr/W, Sr/Nb,Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca, Bi/Sn, Bi/Sb, Ge/Hf, Hf/Sm, Sb/Ag,Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W, Sb/Hf, Sb/Yb, Sb/Sn, Yb/Au, Yb/Ta,Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag, Au/Sr, W/Ge, Ta/Hf, W/Au, Ca/W, Au/Re,Sm/Li, La/K, Zn/Cs, Zr/Cs, Ca/Ce, Li/Sr, Cs/Zn, Dy/K, La/Mg, In/Sr,Sr/Cs, Ga/Cs, Lu/Fe, Sr/Tm, La/Dy, Mg/K, Zr/K, Li/Cs, Sm/Cs, In/K,Lu/Tl, Pr/Zn, Lu/Nb, Na/Pt, Na/Ce, Ba/Ta, Cu/Sn, Ag/Au, Al/Bi, Al/Mo,Al/Nb, Au/Pt, Ga/Bi, Mg/W, Pb/Au, Sn/Mg, Zn/Bi, Gd/Ho, Zr/Bi, Ho/Sr,Ca/Sr, Sr/Pb or Sr/Hf.
 9. The method of claim 1, wherein the catalystcomprises a combination of at least three different doping elements. 10.The method of claim 9, wherein the three different doping elements areselected from Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf,Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi,Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn,Ir, As, Li, Tb, Er, Te and Mo.
 11. The method of claim 1, wherein thecatalyst comprises a combination of at least four different dopingelements.
 12. The method of claim 11, wherein the four different dopingelements are selected from Na, Mg, Ca, Sr, Ga, Sc, Y, Zr, In, Nd, Eu,Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb, Ba, Yb, Ni, Lu,Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al, Tl, Pr, Co, Rh,Ti, V, Cr, Mn, Ir, As, Li, Tb, Er, Te and Mo.
 13. The method of claim 1,wherein Ln1 or Ln2 is lanthanum.
 14. The method of claim 1, wherein Ln1or Ln2 is neodymium.
 15. The method of claim 1, wherein Ln1 or Ln2 isytterbium.
 16. The method of claim 1, wherein Ln1 or Ln2 is europium.17. The method of claim 1, wherein Ln1 or Ln2 is samarium.
 18. Themethod of claim 1, wherein Ln1 or Ln2 is cerium.
 19. The method of claim1, wherein Ln1 or Ln2 is praseodymium.
 20. The method of claim 1,wherein the catalytic material is contacted with the gas at atemperature less than 800° C.
 21. The method of claim 1, wherein thecatalytic material is contacted with the gas at a temperature less than700° C.
 22. The method of claim 1, having a conversion of methane toethylene of greater than 10%.
 23. The method of claim 1, having a yieldof ethylene of greater than 10%.
 24. The method of claim 1, having aconversion of methane of greater than 10%.
 25. The method of claim 1,having a C2 yield of greater than 10%.
 26. A method for the preparationof ethane, ethylene or combinations thereof, the method comprisingcontacting a catalyst with a gas comprising methane, the catalystcomprising an oxide of a rare earth element, wherein the oxide of a rareearth element is a metal oxyhydroxide, metal oxyhalide, a metaloxynitrate or a metal phosphate, wherein the catalyst further comprisesat least one doping element from groups 1-16, lanthanides, actinides orcombinations thereof, wherein the catalyst comprises a C2 selectivity ofgreater than 50% and a methane conversion of greater than 20% when thecatalyst is employed as a heterogeneous catalyst in the oxidativecoupling of methane at a temperature of 750° C. or less.
 27. The methodof claim 26, wherein the at least one doping element is selected fromgroups 1-4, 8, 13, 14, lanthanides, actinides and combinations thereof.28. The method of claim 26, wherein the at least one doping element isselected from groups 1-6, 8, 11, 13-15, lanthanides, actinides andcombinations thereof.
 29. The method of claim 26, wherein the at leastone doping element is a rare earth element.
 30. The method of claim 26,wherein the at least one doping element is Na, Mg, Ca, Sr, Ga, Sc, Y,Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S, Zn, Rb,Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re, Fe, Al,Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb, Er, Te or Mo.
 31. Themethod of claim 26, wherein the catalyst comprises a combination of atleast two different doping elements.
 32. The method of claim 31, whereinthe two different doping elements are selected from Na, Mg, Ca, Sr, Ga,Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S,Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re,Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb, Er, Te and Mo.33. The method of claim 31, wherein the combination of at least twodifferent doping elements is La/Nd, La/Sm, La/Ce, La/Sr, Eu/Na, Eu/Gd,Ca/Na, Eu/Sm, Eu/Sr, Mg/Sr, Ce/Mg, Gd/Sm, Sr/W, Sr/Ta, Au/Re, Au/Pb,Bi/Hf, Sr/Sn or Mg/N, Ca/S, Rb/S, Sr/Nd, Eu/Y, Mg/Nd, Sr/Na, Nd/Mg,La/Mg, Yb/S, Mg/Na, Sr/W, K/La, K/Na, Li/Cs, Li/Na, Zn/K, Li/K, Rb/Hf,Ca/Cs, Hf/Bi, Sr/Sn, Sr/W, Sr/Nb, Zr/W, Y/W, Na/W, Bi/W, Bi/Cs, Bi/Ca,Bi/Sn, Bi/Sb, Ge/Hf, Hf/Sm, Sb/Ag, Sb/Bi, Sb/Au, Sb/Sm, Sb/Sr, Sb/W,Sb/Hf, Sb/Yb, Sb/Sn, Yb/Au, Yb/Ta, Yb/W, Yb/Sr, Yb/Pb, Yb/W, Yb/Ag,Au/Sr, W/Ge, Ta/Hf, W/Au, Ca/W, Au/Re, Sm/Li, La/K, Zn/Cs, Zr/Cs, Ca/Ce,Li/Sr, Cs/Zn, Dy/K, La/Mg, In/Sr, Sr/Cs, Ga/Cs, Lu/Fe, Sr/Tm, La/Dy,Mg/K, Zr/K, Li/Cs, Sm/Cs, In/K, Lu/Tl, Pr/Zn, Lu/Nb, Na/Pt, Na/Ce,Ba/Ta, Cu/Sn, Ag/Au, Al/Bi, Al/Mo, Al/Nb, Au/Pt, Ga/Bi, Mg/W, Pb/Au,Sn/Mg, Zn/Bi, Gd/Ho, Zr/Bi, Ho/Sr, Ca/Sr, Sr/Pb or Sr/Hf.
 34. The methodof claim 26, wherein the catalyst comprises a combination of at leastthree different doping elements.
 35. The method of claim 34, wherein thethree different doping elements are selected from Na, Mg, Ca, Sr, Ga,Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In, Cs, S,Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au, Pb, Re,Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb, Er, Te and Mo.36. The method of claim 26, wherein the catalyst comprises a combinationof at least four different doping elements.
 37. The method of claim 36,wherein the four different doping elements are selected from Na, Mg, Ca,Sr, Ga, Sc, Y, Zr, In, Nd, Eu, Sm, Ce, Gd, Hf, Ho, Tm, W, La, K, Dy, In,Cs, S, Zn, Rb, Ba, Yb, Ni, Lu, Ta, P, Pt, Bi, Sn, Nb, Sb, Ge, Ag, Au,Pb, Re, Fe, Al, Tl, Pr, Co, Rh, Ti, V, Cr, Mn, Ir, As, Li, Tb, Er, Teand Mo.
 38. The method of claim 26, wherein the oxide of a rare earthelement is a lanthanum oxyhydroxide, a lanthanum oxyhalide, a lanthanumoxynitrate or a lanthanum phosphate.
 39. The method of claim 26, whereinthe oxide of a rare earth element is a neodymium oxyhydroxide, aneodymium oxyhalide, a neodymium oxynitrate or a neodymium phosphate.40. The method of claim 26, wherein the oxide of a rare earth element isa ytterbium oxyhydroxide, a ytterbium oxyhalide, a ytterbium oxynitrateor a ytterbium phosphate.
 41. The method of claim 26, wherein the oxideof a rare earth element is a europium oxyhydroxide, a europiumoxyhalide, a europium oxynitrate or a europium phosphate.
 42. The methodof claim 26, wherein the oxide of a rare earth element is a samariumoxyhydroxide, a samarium oxyhalide, a samarium oxynitrate or a samariumphosphate.
 43. The method of claim 26, wherein the oxide of a rare earthelement is a yttrium oxyhydroxide, a yttrium oxyhalide, a yttriumoxynitrate or a yttrium phosphate.
 44. The method of claim 26, whereinthe oxide of a rare earth element is a cerium oxyhydroxide, a ceriumoxyhalide, a cerium oxynitrate or a cerium phosphate.
 45. The method ofclaim 26, wherein the oxide of a rare earth element is a praseodymiumoxyhydroxide, a praseodymium oxyhalide, a praseodymium oxynitrate or apraseodymium phosphate.
 46. The method of claim 26, wherein thecatalytic material is contacted with the gas at a temperature less than800° C.
 47. The method of claim 26, wherein the catalytic material iscontacted with the gas at a temperature less than 700° C.
 48. The methodof claim 26, having a conversion of methane to ethylene of greater than10%.
 49. The method of claim 26, having a yield of ethylene of greaterthan 10%.
 50. The method of claim 26, having a conversion of methane ofgreater than 10%.
 51. The method of claim 26, having a C2 yield ofgreater than 10%.